Molecular dynamics simulation and 3D-pharmacophore analysis of new quinoline-based analogues with dual potential against EGFR and VEGFR-2.

Epidermal growth factor and vascular endothelial growth factor-2 are important targets of tyrosine kinase for the treatment of various cancerous diseases. Combination of inhibition of both targets to produce synergy in the signal pathway is a critical approach to identify novel tyrosine kinase inhibitors. In this study, a series of new compounds derived from the 4-aminoquinoline as dual inhibitors were synthesized. The obtained results of cytotoxicity assay against human carcinoma cell lines indicated 0.8 µM for 4c against A549 showing its high efficiency in comparison to erlotinib. Pharmacophore modeling as a structure-based method was investigated on dual inhibitors and 4c which was compared with co-crystallized in the active site of EGFR and VEGFR-2. They have shown the same binding orientation as vandetanib, erlotinib and sorafenib. Molecular dynamics simulation results approved that Met769, Lys721, Asp1046, and Lys868 are key residues in two binding sites for dual activity. Ala1050 and Pro968 were identified as new amino acid interaction sites for dual inhibition. 4c showed more favorable stability than vandetanib in VEGFR-2 receptor for a 50 ns dynamic simulation. The high correlation between essential pharmacophoric features of designed compounds and lead inhibitors interactions provided a deeper insight into the structural basis of 4-aminoquinoline inhibition.

Pharmacological evaluation of a novel assay for detecting glycine transporter 1 inhibitors and their antipsychotic potential.

Multiple lines of evidence support the notion that hypofunction of glutamatergic neurotransmission is involved in the pathophysiology of schizophrenia. Moreover, glycine and glycine modulators have beneficial effects in patients with schizophrenia, particularly when added on to existing therapy. As glycine is an obligatory co-agonist at the NR1 subunit of the NMDA receptor, blockade of glycine uptake at the glycine transporter type-1 (GlyT1) can enhance low glutamatergic tone. L-687,414 is an antagonist at the glycine modulatory site of the NMDA complex and, behaviorally, increases locomotion. A series of GlyT1 inhibitors along with other psychoactive compounds were examined for their ability to enhance or inhibit the action of L-687,414. GlyT1 inhibitors and the other compounds were examined initially for effects on [(3)H]-glycine uptake in CHO cells expressing hGlyT1b cDNA and for their ability to displace the NMDA-glycine site ligand [(3)H]-L-689,560 from isolated rat forebrain membrane preparations. The in vivo activity of these compounds was determined in mice by measuring their ability to prevent L-687,414-induced hyperlocomotion. GlyT1 inhibitors blocked [(3)H]-glycine uptake in cells expressing the human transporter; other compounds had little or no activity. None of the compounds had affinity for the glycine site of the NMDA receptor complex. Hyperlocomotion induced by L-687,414 was dose-dependently reduced by GlyT1 inhibitors and antipsychotic drugs but not by morphine, fluoxetine or a moderate dose of diazepam. Therefore, this behavioral approach can reliably detect GlyT1 inhibitors which, in turn, may have some activity in common with drugs having antipsychotic effects.

Selective impairment of TLR-mediated innate immunity in human newborns: neonatal blood plasma reduces monocyte TNF-alpha induction by bacterial lipopeptides, lipopolysaccharide, and imiquimod, but preserves the response to R-848.

Newborns are at increased risk of overwhelming infection, yet the mechanisms underlying this susceptibility are incompletely defined. In this study we report a striking 1- to 3-log decrease in sensitivity of monocytes in human neonatal cord blood, compared with monocytes in adult peripheral blood, to the TNF-alpha-inducing effect of multiple TLR ligands, including bacterial lipopeptides (BLPs), LPS, and the imidazoquinoline compound, imiquimod. In marked contrast, TNF-alpha release in response to R-848, a TLR ligand that is a congener of imiquimod, was equivalent in newborn and adult blood. Differences in ligand-induced TNF-alpha release correlated with divergent ligand-induced changes in monocyte TNF-alpha mRNA levels. Newborn and adult monocytes did not differ in basal mRNA or protein expression of TLRs or mRNA expression of functionally related molecules. Newborn monocytes demonstrated diminished LPS-induced, but equivalent R-848-induced, phosphorylation of p38 mitogen-activated protein kinase and altered BLP- and LPS-induced acute modulation of cognate receptors, suggesting that the mechanism accounting for the observed differences may be localized proximal to ligand recognition by surface TLRs. Remarkably, newborn plasma conferred substantially reduced BLP-, LPS-, and imiquimod-induced TNF-alpha release on adult monocytes without any effect on R-848-induced TNF-alpha release, reflecting differences in a plasma factor(s) distinct from soluble CD14. Impaired response to multiple TLR ligands may significantly contribute to immature neonatal immunity. Conversely, relative preservation of responses to R-848 may present unique opportunities for augmenting innate and acquired immunity in the human newborn.

Quantitative structure-activity relationship of flavonoids for inhibition of heterocyclic amine mutagenicity.

The mutagenic/carcinogenic heterocyclic amines formed during the cooking of protein foods have been determined to be a potential risk to human health. Therefore, mitigation measures are beginning to be studied. A recent finding is that the induction of mutation in Salmonella by these amines can be inhibited by the addition of flavonoids to the assay. This study combines data on the inhibitory process with structural, ab initio quantum chemical, hydropathic, and antioxidant factors to develop a quantitative structure-activity relationship (QSAR) database and statistical analysis. For 39 diverse flavonoids the inhibitory potency varied approximately 100-fold. Three predictive variables, in order of decreasing contribution to variance, are: (1) a large dipole moment; (2) after geometric minimization of energy, a small departure from planarity (i.e., small dihedral angle between the benzopyran nucleus and the attached phenyl ring), and a low rotational energy barrier to achieving planarity; and (3) fewer hydroxyl groups on the phenyl ring. However, these variables account for less than half of the variance in inhibitory potency of the flavonoids. Frontier orbital energies and antioxidant or radical scavenging properties showed little or no relationship to potency. We conclude that interference by the flavonoids with cytochrome P450 activation of the promutagens is the probable mechanism for inhibition of mutagenesis, and suggest avenues for further research. Environ. Mol. Mutagen. 35:279-299, 2000 Published 2000 Wiley-Liss, Inc.

8-Aminoquinolines as anticoccidials--II.

During a chemistry program aimed at finding a novel analogue of pentaquine with improved in vivo activity, a number of hypotheses concerning the way this drug acts in the chicken were investigated. Consideration of the products of monoamine oxidase metabolism of pentaquine suggested that pentaquine aldehyde is the likely active metabolite. Although isolation of this unstable compound was not possible, oxime and cyclic acetal and ketal derivatives were obtained and shown to possess in vitro anticoccidial activity.

Carbon monoxide enhances human neutrophil migration in a cyclic GMP-dependent way.

Carbon monoxide (CO) enhanced random migration of human neutrophils. An optimally stimulatory effect was observed with 10 microM CO. CO caused a rapid and transient increase in intracellular level of guanosine-3',5'-cyclic monophosphate (cGMP). The enhancing effect of CO on random migration was reversed to a large extent by inhibitors of cGMP accumulation, and by antagonists of cGMP-dependent protein kinase (G-kinase). These results strongly suggest that the enhancement of random migration by CO is mediated by cGMP and G-kinase. Using hemoglobin, a scavenger of CO, we could show that stimulation of soluble guanylate cyclase over an extended period of time, rather than the observed fast and transient increase in intracellular cGMP levels, is responsible for CO-activated migration. We postulate that CO, like nitric oxide (NO), acts as a biological signal in the immune system.

Hydroxyl radical-dependent inactivation of guanylate cyclase in cerebral arterioles by methylene blue and by LY83583.

BACKGROUND AND PURPOSE: Methylene blue and 6-anilino,5,8-quinolinedione (LY83583) are used extensively to block activation of guanylate cyclase. Both agents generate oxygen radicals. Therefore, it appeared profitable to investigate whether the generation of oxygen radicals by these agents is responsible for the blockade of responses to nitrodilators that act via activation of guanylate cyclase to relax vascular smooth muscle and cause vasodilation. METHODS: We tested in anesthetized cats equipped with cranial windows responses to topical application of nitroglycerin, nitroprusside, and adenosine before and during topical application of methylene blue (5 microM). Responses to the vasoactive agents were tested during application of methylene blue after permeabilization of the cell membrane with a detergent to allow methylene blue to enter vascular smooth muscle. Responses were also tested in the presence of superoxide dismutase, catalase, deferoxamine, or dimethyl sulfoxide to scavenge reactive products of oxygen metabolism or to eliminate catalytic iron. In additional experiments we tested the effects of topical application of nitroprusside or adenosine before and after application of LY83583. The responses to the vasoactive agents were also tested in the presence of superoxide dismutase, catalase, or dimethyl sulfoxide in addition to LY83583. We also tested responses to calcitonin gene-related peptide before and in the presence of LY83583 with or without superoxide dismutase. RESULTS: Methylene blue eliminated the arteriolar dilation in response to nitroprusside and nitroglycerin after permeabilization of the cell membrane with a detergent but not before. The responses to adenosine were unaffected. The blockade induced by methylene blue was reversed by superoxide dismutase, catalase, or dimethyl sulfoxide but not by deferoxamine. LY83583 blocked responses to nitroprusside but not to adenosine. The blockade was eliminated by superoxide dismutase, catalase, or dimethyl sulfoxide. LY83583 blocked the vasodilation induced by calcitonin gene-related peptide. This blockade was reversed by superoxide dismutase. CONCLUSIONS: Methylene blue and LY83583 prevent the activation of soluble guanylate cyclase by nitrodilators or by calcitonin gene-related peptide by generating oxygen radicals. The mediator of this response is the hydroxyl radical. Methylene blue does not enter the vascular smooth muscle of cerebral arterioles unless the cell membrane is permeabilized.

[The resistance of Plasmodium falciparum strains to preparations of the 4-aminoquinoline series in the Republic of Guinea]. / Rezistentnost' shtammov Plasmodium falciparum k preparatam 4-aminokhinolinovogo riada v Gvineiskoi Respublike.

In vivo measurements of P. falciparum sensitivity to chloroquine diphosphate, carried out in the Republic of Guinea, resulted in isolation of strains with degrees I and II resistance from 5 of the 25 examined patients, that may be due to a wide prophylactic administration of the drug to all patients with fevers without completing the course of therapy in all the patients infected. Such courses are obligatory to prevent the dissemination of chloroquine-resistant strains of the parasite and augmentation of the resistance. Further use of chloroquine and its analogs for the prevention and chemoprophylaxis of malaria in the Republic of Guinea appears still desirable, because the majority of P. falciparum strains are still sensitive to these agents. If no favorable changes are detectable in the clinical parameters of malaria patients in 4-5 days of chloroquine treatment or the condition recurs in 1.5-2 months, assessment of P. falciparum sensitivity to chloroquine is advisable, followed by a rational choice of the drug.

Leukocyte and platelet-derived factors augment canine coronary constriction to serotonin.

In open-chest anesthetized dogs acute hypertension causes neutrophil and platelet adhesion to vascular endothelium and selectively potentiates constriction to serotonin in proximal coronary arteries. To examine underlying mechanisms, canine left anterior descending coronary arteries subjected to 15 min hypertension (LAD-HYP) and control left circumflex coronary arteries (CX) perfused at normal pressure were studied in organ chambers. In endothelium-intact LAD-HYP rings, constriction to serotonin was potentiated fourfold compared with control CX rings but was similar in denuded LAD-HYP and CX vessels. Endothelium-dependent relaxation to acetylcholine was not affected by acute hypertension. In LAD-HYP rings 10 microM LY 83583 (which depletes guanosine 3',5'-cyclic monophosphate and inhibits effects of endothelium-derived relaxing factor) augmented constriction to serotonin twofold. LY 83583 did not affect the serotonin response in hypertensive rings whose endothelium was mechanically removed. Blockade of either leukotriene D4 (LTD4) receptors (either with LY 171883 or SKF 102992) or thromboxane A2 (TxA2) receptors (with SQ 29548) partially blunted constriction to serotonin. Combined LTD4- and TxA2-receptor blockade completely normalized serotonin-induced constriction in LAD-HYP rings. In preconstricted LAD-HYP rings, relaxations to serotonin were markedly impaired but were restored by addition of ketanserin. Normalization of relaxation to serotonin in hypertensive vessels by ketanserin is likely due to inhibition of 5-hydroxytryptamine2 (5-HT2) receptors on platelet membranes. In conclusion, augmented constriction to serotonin in canine epicardial vessels exposed to acute hypertension is not due to an impairment of endothelium-dependent relaxation to the amine but to concomitant release of leukotrienes and TxA2 from leukocytes and platelets adhering to damaged endothelium. Activation of 5-HT2 serotonergic receptors on platelet membranes could be a possible trigger mechanism.