New ligands at the melatonin binding site MT3

The third melatonin binding site, MT3 is a non-classical one since it is not a seven transmembrane domains receptor, but an enzyme, quinone reductase 2. A major concern for the study of the physiological role of this site is the lack of specific ligands, permitting to more accurately dissect the pathways linked to the activation of MT3. Indeed, in the course of finding new ligands, we identified a new series of compounds with affinity to the binding site in the nM range, particularly 2,3-dimethoxy 7-hydroxy 10-methyl 5H 10H indeno(1,2-b)indol-10-one (DMHMIO), with a Ki of 190 pM. Based on slightly different and novel synthons compared to most of the compounds used in melatonin pharmacology studies, these compounds offer new perspective for the description of the melatonin pathways, so much more by not having any affinity towards the MT1 and MT2 'classical' melatonin receptors.

Novel antitumor indenoindole derivatives targeting DNA and topoisomerase II

We have identified a novel series of indenoindole derivatives endowed with potent cytotoxic activities toward cancer cells. Five compounds containing a 8-[2-(dialkylamino)ethoxy]-2,3-dimethoxy-5H-10H-indeno[1,2-b]indol-10-one-O-propynyl-oxime core substituted with a phenyl, furanyl, or a methyl substituent on the propynyl side chain have been synthesized and their mechanism of action was investigated using a panel of complementary biophysical and biochemical techniques. The compounds were shown to intercalate into DNA with a preference for AT-rich sequences. They have no effect on topoisomerase I but they strongly stimulate DNA cleavage by topoisomerase II. Their capacity to stabilize topoisomerase II-DNA covalent complexes is comparable to that of the reference drug etoposide. The nature and orientation of the substituent on the propynyl chain modulate the DNA binding and topoisomerase II inhibitory properties of the compounds and, apparently, there is a correlation between the cytotoxic potential and the molecular action at the DNA-topoisomerase II level. The growth of human K562 leukemia cells is strongly reduced in the presence of the indenoindoles (IC(50) in the 50nM range) which maintain a high cytotoxic activity toward the adriamycin-resistant K562adr cells line in vitro. The low resistance indexes measured with the indenoindoles (RRI = 10-30) compared to adriamycin (RRI = 1000) suggest that our new compounds are weakly or not sensitive to drug efflux mediated by glycoprotein-P and/or multidrug resistance (MDR) protein pumps. Finally, we also show that these indenoindoles arrest K562 cells in the G2/M phase of the cell cycle and promote apoptosis, as indicated by the appearance of internucleosomal DNA cleavage. One compound in the series was tested for in vivo antitumor activity against the colon 38 model and at 25mg/kg it showed 100% complete tumor regression in the treated mice, without significant body weight loss. Altogether, the results reported here establish that our indenoindole derivatives represent a novel interesting series of DNA-targeted cytotoxic agents.

[3H]BHDP as a novel and selective ligand for sigma1 receptors in liver mitochondria and brain synaptosomes of the rat

The binding profile of [(3)H]BHDP ([(3)H]N-benzyl-N'-(2-hydroxy-3,4-dimethoxybenzyl)-piperazine) was evaluated. [(3)H]BHDP labelled a single class of binding sites with high affinity (K(d)=2-3 nM) in rat liver mitochondria and synaptic membranes. The pharmacological characterization of these sites using sigma reference compounds revealed that these sites are sigma receptors and, more particularly, sigma1 receptors. Indeed, BHDP inhibited [(3)H]pentazocine binding, a marker for sigma1 receptors, with high affinity in a competitive manner. BHDP is selective for sigma1 receptors since it did not show any relevant affinity for most of the other receptors, ion channels or transporters tested. Moreover, in an in vitro model of cellular hypoxia, BHDP prevented the fall in adenosine triphosphate (ATP) levels caused by 24 h hypoxia in cultured astrocytes. Taken together, these results demonstrate that [(3)H]BHDP is a potent and selective ligand for sigma1 receptors showing cytoprotective effects in astrocytes.

S17834, a new inhibitor of cell adhesion and atherosclerosis that targets nadph oxidase

microdant stress is involved in the events that accompany endothelial cell expression of adhesion molecules and leukocyte adherence in many disease states, including atherosclerosis. A recently discovered benzo(b)pyran-4-one derivative, S17834 (10 to 50 micromol/L), reduced tumor necrosis factor-stimulated vascular cell adhesion molecule-1 (VCAM) mRNA accumulation and protein expression in human umbilical vein endothelial cells. Intercellular cell adhesion molecule-1 and E-selectin were also inhibited by S17834, but platelet endothelial cell adhesion molecule-1 was not. Adherence of U937 monocytic cells to the endothelial cells as well as to plastic plates coated with soluble VCAM, intercellular cell adhesion molecule-1, P-selectin, and E-selectin was also decreased. Consistent with an antioxidant mechanism of action, S17834 (10 to 50 micromol/L) inhibited tumor necrosis factor-stimulated release of superoxide from endothelial cells measured by cytochrome c reduction. S17834 had no effect on superoxide produced by xanthine oxidase, indicating that rather than by acting as a scavenger of superoxide anion, the drug acts by inhibiting the production of free radicals. Indeed, S17834 inhibited NADPH oxidase activity of endothelial cell membranes. The ability to inhibit superoxide anion production appears to be key in the effect of S17834 on superoxide anion production and VCAM expression, because these actions were mimicked by adenovirus-mediated overexpression of superoxide dismutase. Furthermore, these actions may be relevant in vivo, because S17834 reduced aortic superoxide anion levels by 40% and aortic atherosclerotic lesions by 60% in apolipoprotein E-deficient mice. These results indicate that S17834 inhibits adhesion molecule expression and adherence of leukocytes to endothelial cells as well as aortic atherogenesis and that perhaps these effects can be explained by its ability to inhibit endogenous superoxide anion production.

Preparation and pharmacological profile of 2-trifluoromethyl-benzo(8,9)-1,3-diaza-spiro (4,6)-undeca-2,8-diene and its enantiomers as new anti-obesity agents

Obesity affects a large population of industrialised countries in which occurrence may reach 20%. The multifactorial aspect of the pathology prompted us to develop new entities associating favourable effects on both eating behaviour and metabolic parameters. The 2-trifluoromethyl-benzocyloheptene moiety has been combined with an imidazoline ring for synthesising a new anti-obesity agent. Preparation of the already known 2-trifluoromethyl-5-H-6,7,8,9-tetrahydro-benzocyclohepten-7-one as a key intermediate has been significantly improved, and an enantioselective procedure has been developed for imidazoline construction. The syntheses and pharmacological profiles of the compounds are presented here, particularly the effects on eating behaviour and body weight, and the putative involvement of the L-enantiomer in the treatment of metabolic diseases.

Amino derivatives of phenyl alkyl thiophene as inhibitors of bone resorption. Structure-activity relationship

Metabolism of arachidonic acid through the 5-lipoxygenase (LO) pathway generates compounds that stimulate osteoclastic bone resorption; since LO metabolites might play a role in bone loss due to excessive resorption it was tried to develop a series of antiresorptive agents starting from an already known LO inhibitor. Of the 35 compounds synthesized, 11 strongly inhibited (10 mumol/l) retinoic acid-induced bone resorption in cultured mouse calvariae; they were also tested for their effect on LO activity using rat peritoneal neutrophils, but no correlation could be drawn between inhibition of LO and bone resorption. Other pathways, still to be identified, must therefore be targeted by these compounds even though LO inhibition might contribute to their effects on bone. Two compounds selected for further studies were found active on parathyroid hormone-induced osteolysis, while they had no effect on basal resorption; they must, therefore, act at some key point in the process of activation of osteoclastic resorption. This series of compounds may represent a new way for the treatment of bone loss due to excessive resorption.