Synthesis and MEK1 inhibitory activities of imido-substituted 2-chloro-1,4-naphthoquinones

The one-pot synthesis of amidonapthoquinones from aminonaphthoquinones

Described here is a one-pot method of synthesizing amidonaphthoquinones from the corresponding aminonaphthoquinones. The scope of amides that can be synthesized using this methodology is relatively broad and the yield of product is higher than the traditional methods of synthesizing these substrates.

Novel drug design for Chagas disease via targeting Trypanosoma cruzi tubulin: Homology modeling and binding pocket prediction on Trypanosoma cruzi tubulin polymerization inhibition by naphthoquinone derivatives

Chagas disease, also called American trypanosomiasis, is a parasitic disease caused by Trypanosoma cruzi (T. cruzi). Recent findings have underscored the abundance of the causative organism, (T. cruzi), especially in the southern tier states of the US and the risk burden for the rural farming communities there. Due to a lack of safe and effective drugs, there is an urgent need for novel therapeutic options for treating Chagas disease. We report here our first scientific effort to pursue a novel drug design for treating Chagas disease via the targeting of T. cruzi tubulin. First, the anti T. cruzi tubulin activities of five naphthoquinone derivatives were determined and correlated to their anti-trypanosomal activities. The correlation between the ligand activities against the T. cruzi organism and their tubulin inhibitory activities was very strong with a Pearson's r value of 0.88 (P value <0.05), indicating that this class of compounds could inhibit the activity of the trypanosome organism via T. cruzi tubulin polymerization inhibition. Subsequent molecular modeling studies were carried out to understand the mechanisms of the anti-tubulin activities, wherein, the homology model of T. cruzi tubulin dimer was generated and the putative binding site of naphthoquinone derivatives was predicted. The correlation coefficient for ligand anti-tubulin activities and their binding energies at the putative pocket was found to be r=0.79, a high correlation efficiency that was not replicated in contiguous candidate pockets. The homology model of T. cruzi tubulin and the identification of its putative binding site lay a solid ground for further structure based drug design, including molecular docking and pharmacophore analysis. This study presents a new opportunity for designing potent and selective drugs for Chagas disease.

Forecasting cell death dose-response from early signal transduction responses in vitro

The rapid pharmacodynamic response of cells to toxic xenobiotics is primarily coordinated by signal transduction networks, which follow a simple framework: the phosphorylation/dephosphorylation cycle mediated by kinases and phosphatases. However, the time course from initial pharmacodynamic response(s) to cell death following exposure can have a vast range. Viewing this time lag between early signaling events and the ultimate cellular response as an opportunity, we hypothesize that monitoring the phosphorylation of proteins related to cell death and survival pathways at key, early time points may be used to forecast a cell's eventual fate, provided that we can measure and accurately interpret the protein responses. In this paper, we focused on a three-phased approach to forecast cell death after exposure: (1) determine time points relevant to important signaling events (protein phosphorylation) by using estimations of adenosine triphosphate production to reflect the relationship between mitochondrial-driven energy metabolism and kinase response, (2) experimentally determine phosphorylation values for proteins related to cell death and/or survival pathways at these significant time points, and (3) use cluster analysis to predict the dose-response relationship between cellular exposure to a xenobiotic and plasma membrane degradation at 24 h post-exposure. To test this approach, we exposed HepG2 cells to two disparate treatments: a GSK-3β inhibitor and a MEK inhibitor. After using our three-phased approach, we were able to accurately forecast the 24 h HepG2 plasma membrane degradation dose-response from protein phosphorylation values as early as 20 min post-MEK inhibitor exposure and 40 min post-GSK-3β exposure.

2-Chloro-N-(2-chloro-benzo-yl)-N-(2-ethyl-4-oxo-3,4-di-hydro-quinazolin-3-yl)benzamide

In the title compound, C24H17Cl2N3O3, the quinazolinone ring system is close to planar (r.m.s. deviation = 0.0132 Å), with the imide unit almost perpendicular to it, subtending a dihedral angle of 89.1 (1)°. However, the imide unit itself is not planar, the dihedral angle between the two O=C-N components being 34.6 (1)°. The dihedral angle between the two chlorobenzene rings is 40.50 (7)°, while the angles between these rings and the imide moiety are 54.6 (1) and 58.2 (1)°, respectively. The dihedral angles between the 2-chloro-phenyl rings and the quinazolinone ring system are 48.77 (5) and 32.92 (7)° for rings A and B, respectively. In the crystal, weak C-H⋯O inter-actions link the mol-ecules into a three-dimensional array.

N-(3-Chloro-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-N-propionylpropionamide

In the title molecule, C16H14ClNO4, the four essentially planar atoms of the imide group [r.m.s. deviation = 0.0286 (11) Å] form a dihedral angle of 77.36 (13)° with the naphthoquinone group [maximun deviation = 0.111 (2) Å for the carbonyl O atom in the naphthalene 1-position] and the two imide carbonyl groups are orientedantiwith respect to each other. In the crystal, molecules are connected by weak C—H...O hydrogen bonds, as well as π–π stacking interactions [centroid–centroid distance = 3.888 (3) Å], forming a three-dimensional network.

N-Butanoyl-N-(3-chloro-1,4-dioxonaphthalen-2-yl)butanamide

In the title compound, C₁₈H₁₈ClNO₄, the imide group with its two alkyl substituents is approximately perpendicular to the plane of the naphtho­quinone ring system [dihedral angle = 78.5 (1)°]. Further, the imide carbonyl groups are oriented in an anti sense. In the crystal, the substituted naphtho­quinone rings form π–π stacks in the a-axis direction [perpendicular centroid–centroid distance = 3.209 (2) Å and slippage = 4.401 Å].

Synthesis and characterization of novel unsymmetrical and symmetrical 3-halo- or 3-methoxy-substituted 2-dibenzoylamino-1,4-naphthoquinone derivatives

Symmetrical and unsymmetrical 3-halo- or 3-methoxy- substituted 2-dibenzoylamino- 1,4-naphthoquinone analogs were synthesized with an average yield of 45% via sodium hydride promoted bis-acylation of 2-amino-3-chloro-1,4-naphthoquinone, 2-amino-3-bromo-1,4-naphthoquinone and 2-amino-3-methoxy-1,4-naphthoquinone.

Spectroscopic and theoretical studies on the nucleophilic substitution of 2,3-dichloronaphthoquinone with para-substituted anilines in solid state via initial charge transfer complexation

Various spectroscopy techniques (UV-Vis, DRS, FT-IR, (1)H NMR, LC-MS) and theoretical computations have been employed to investigate the mechanism of the nucleophilic substitution reaction of 2,3-dichloronaphthoquinone (DCNQ) with para-substituted anilines in solid state under base- and solvent-free conditions against traditional synthetic routes. The initial formations of electron donor acceptor (EDA) adduct between DCNQ and aniline was found to be the driving force for the substitution reaction to occur in solid phase.

N-(1,4-Dioxo-1,4-dihydro-naphthalen-2-yl)benzamide

The title compound, C(17)H(11)NO(3), was an inter-mediate synthesized during bis-acyl-ation of 2-amino-1,4-naphtho-quinone with benzoyl chloride. A mixture of block- and needle-shaped crystals were obtained after column chromatography. The block-shaped crystals were identified as the imide and the needles were the title amide. The naphtho-quinone scaffold is roughly planar (r.m.s. deviation = 0.047 Å for the C atoms). The N-H and C=O bonds of the amide group are anti to each other. A dihedral angle between the naphtho-quinone ring system and the amide group of 3.56 (3)°, accompanied by a dihedral angle between the amide group and the phenyl group of 9.51 (3)°, makes the naphtho-quinone ring essentially coplanar with the phenyl ring [dihedral angle = 7.12 (1)°]. In the crystal, molecules are linked by a weak N-H⋯O hydrogen bond and by two weak C-H⋯O interactions leading to the formation of zigzag chains along [010].

N-Benzoyl-N-(1,4-dioxonaphthalen-2-yl)benzamide

The title mol-ecule, C(24)H(15)NO(4), crystallizes with two mol-ecules in the asymmetric unit (Z' = 2). For both mol-ecules, the two amide groups are not coplanar, as the dihedral angles of the respective NCO groups are similar at 50.37 (14) and 51.22 (13)°. However, the orientations of the substituent phenyl rings with the central naphthalene system are significantly different for the two mol-ecules; for one mol-ecule, these dihedral angles are 80.29 (3) and 80.95 (4)°, while for the second mol-ecule they are 86.63 (3) and 72.82 (4)°. The crystal packing shows the mol-ecules to be linked by weak C-H⋯O inter-actions.

Antitrypanosomal activities and cytotoxicity of some novel imido-substituted 1,4-naphthoquinone derivatives

The antitrypanosomal activities, cytotoxicity, and selectivity indices of eleven imido-substituted 1,4-naphthoquinone derivatives and nifurtimox have been studied. Compared to nifurtimox (IC(50) = 10.67 μM), all the imido-naphthoquinone analogs (IMDNQ1-IMDNQ11) are more potent on Trypanosoma cruzi with IC50 values ranging from 0.7 μM to 6.1 μM (p < 0.05). Studies of the cytotoxic activities of these compounds on a Balb/C 3T3 mouse fibroblast cell line revealed that four of these compounds, IMDNQ1, IMDNQ2, IMDNQ3, and IMDNQ10 displayed selectivity indices of 60.25, 53.97, 31.83, and 275.3, respectively, rendering them significantly (p < 0.05) more selective in inhibiting the parasite growth than nifurtimox (selectivity index = 10.86).

Synthesis and cytotoxic activities of some 2-arylnaphtho[2,3-d]oxazole-4,9-dione derivatives on androgen-dependent (LNCaP) and androgen-independent (PC3) human prostate cancer cell lines

The synthesis of five 2-arylnaphtho[2,3-d]oxazole-4,9-dione derivatives was accomplished by refluxing 2-amino-3-bromo-1,4-naphthoquinone with appropriate benzoyl chloride analogs at elevated temperatures. In vitro anticancer evaluation of these compounds was performed on androgen-dependent, LNCaP, and androgen-independent, PC3, human prostate cancer cell lines. In general, these compounds displayed slightly stronger cytotoxicity on the androgen-dependent LNCaP than on the androgen-independent PC3 prostate cancer cell lines. The meta-substituted 2-(3-Chloro-phenyl)-naphtho[2,3-d]oxazole-4,9-dione (10) appear to display the best cytotoxicity on both cell lines with an IC(50) of 0.03 μM on LNCaP and 0.08 μM on PC3 after 5 days of exposure.

Crystal structures of MEK1 binary and ternary complexes with nucleotides and inhibitors

MEK1 is a member of the MAPK signal transduction pathway that responds to growth factors and cytokines. We have determined that the kinase domain spans residues 35-382 by proteolytic cleavage. The complete kinase domain has been crystallized and its X-ray crystal structure as a complex with magnesium and ATP-gammaS determined at 2.1 A. Unlike crystals of a truncated kinase domain previously published, the crystals of the intact domain can be grown either as a binary complex with a nucleotide or as a ternary complex with a nucleotide and one of a multitude of allosteric inhibitors. Further, the crystals allow for the determination of costructures with ATP competitive inhibitors. We describe the structures of nonphosphorylated MEK1 (npMEK1) binary complexes with ADP and K252a, an ATP-competitive inhibitor (see Table 1), at 1.9 and 2.7 A resolution, respectively. Ternary complexes have also been solved between npMEK1, a nucleotide, and an allosteric non-ATP competitive inhibitor: ATP-gammaS with compound 1 and ADP with either U0126 or the MEK1 clinical candidate PD325089 at 1.8, 2.0, and 2.5 A, respectively. Compound 1 is structurally similar to PD325901. These structures illustrate fundamental differences among various mechanisms of inhibition at the molecular level. Residues 44-51 have previously been shown to play a negative regulatory role in MEK1 activity. The crystal structure of the integral kinase domain provides a structural rationale for the role of these residues. They form helix A and repress enzymatic activity by stabilizing an inactive conformation in which helix C is displaced from its active state position. Finally, the structure provides for the first time a molecular rationale that explains how mutations in MEK may lead to the cardio-facio-cutaneous syndrome.

N-(3-Bromo-1,4-dioxo-1,4-dihydro-2-naphth-yl)-4-fluoro-N-(4-fluoro-benzo-yl)benzamide

In the title compound, C₂₄H₁₂BrF₂NO₄, synthesized from 2-amino-3-bromo-1,4-naphthoquinone and 4-fluoro­benzoyl chloride, the two p-fluoro­phenyl rings are inclined at 73.9 (1) and 73.6 (1)° to the naphthoquinone ring system. The two imido carbonyl O atoms are anti to each other, while the fluoro­phenyl rings are located opposite each other, connected to the imide group in a funnel-like arrangement. This conformation allows the fluorine groups be oriented slightly away from each other. An examination of the packing shows a close inter­molecular F⋯O contact of 2.982 (5) Å and a Br⋯O contact of 2.977 (4) Å. In addition, the mol­ecules are linked by weak inter­molecular C—H⋯O and C—H⋯F inter­actions.

2-Chloro-3-(4-chloro-benzamido)-1,4-naphthoquinone

The naphthoquinone ring is almost perpendicular [dihedral angle 71.02 (3)°] to the phenyl group of the title compound, C(17)H(9)Cl(2)NO(3), while the dihedral angle between the amide group and the 4-chloro-phenyl ring is 21.9 (2)°. The conformation of the N-H and C=O bonds are anti to each other. N-H⋯Cl hydrogen bonds link the mol-ecules into chains in the a-axis direction. In addition, these chains are linked by weak inter-molecular C-H⋯O inter-actions.

N-(3-Bromo-1,4-dioxo-1,4-dihydro-2-naphth-yl)-2-chloro-N-(2-chloro-benzoyl)benzamide

The title compound, C(24)H(12)BrCl(2)NO(4), was synthesized from 2-amino-3-bromo-1,4-naphthoquinone and 2-chloro-benzoyl chloride. The crystal structure shows that each of the chloro-phenyl rings is inclined at about 60° to the naphthoquinone ring system. The two chloro-phenyl rings adopt a conformation that ensures that chlorine substituents are anti so as to reduce electronic repulsion. An examination of the packing shows close O⋯Br and Cl⋯Cl contacts of 2.947 (2) and 3.346 (1) Å, respectively. In addition, the molecules are linked by weak intermolecular C-H⋯O and C-H⋯Cl interactions.

Mitogen-activated protein kinase activity may not be necessary for the neuropathology of Niemann-Pick type C mice

Hyperphosphorylation of neurofilament and tau, and formation of cytoskeletal lesions, are notable features of several human neurodegenerative diseases, including Niemann-Pick Disease Type C (NPC). Previous studies suggested that the MAPKs, extracellular signal regulated kinase 1 and 2 (ERK1/2) may play a significant role in this aspect of NPC. To test this idea, we treated npc mice with PD98059, a specific and potent inhibitor of MAPK activation. Although activity of ERK1/2 was inhibited by 40%, a 2-week intracerebroventricular infusion of PD98059 just prior to onset of cytoskeletal pathology and symptoms in npc mice did not delay or inhibit prominent hallmarks of NPC. Unexpectedly, ERK1/2 inhibition led to aggravation of tau hyperphosphorylation, particularly in oligodendroctyes, in a manner similar to that of certain human tauopathies. Our results suggest that ERK1/2 does not play a major role in NPC neuropathology, and therefore, that MAPK inhibition is unlikely to be a useful strategy for managing the disease.

A systematic interaction map of validated kinase inhibitors with Ser/Thr kinases

Protein kinases play a pivotal role in cell signaling, and dysregulation of many kinases has been linked to disease development. A large number of kinase inhibitors are therefore currently under investigation in clinical trials, and so far seven inhibitors have been approved as anti-cancer drugs. In addition, kinase inhibitors are widely used as specific probes to study cell signaling, but systematic studies describing selectivity of these reagents across a panel of diverse kinases are largely lacking. Here we evaluated the specificity of 156 validated kinase inhibitors, including inhibitors used in clinical trials, against 60 human Ser/Thr kinases using a thermal stability shift assay. Our analysis revealed many unexpected cross-reactivities for inhibitors thought to be specific for certain targets. We also found that certain combinations of active-site residues in the ATP-binding site correlated with the detected ligand promiscuity and that some kinases are highly sensitive to inhibition using diverse chemotypes, suggesting them as preferred intervention points. Our results uncovered also inhibitor cross-reactivities that may lead to alternate clinical applications. For example, LY333'531, a PKCbeta inhibitor currently in phase III clinical trials, efficiently inhibited PIM1 kinase in our screen, a suggested target for treatment of leukemia. We determined the binding mode of this inhibitor by x-ray crystallography and in addition showed that LY333'531 induced cell death and significantly suppressed growth of leukemic cells from acute myeloid leukemia patients.

The effects of intracellular signalling pathway inhibitors on phagocytosis by haemocytes of Manduca sexta

The intracellular signalling pathways activated during phagocytosis by larval haemocytes of a lepidopteran, Manduca sexta, were investigated. Using fluorescein-labelled Escherichia coli as bioparticles, a fluorescence-based assay was used to quantify phagocytosis by haemocytes in monolayers in vitro, and the intracellular signalling pathways involved in phagocytosis were examined using inhibitors. Pathways known to be involved in phagocytosis by mammalian cells were selected for the study in haemocytes, and the amino acid sequences of human isoforms of the selected protein targets were used to conduct searches of two completed databases of insect proteins, those of Drosophila melanogaster and Anopheles gambiae and EST databases of moths Bombyx mori and M. sexta. Decreases in phagocytosis produced by pathway inhibitors indicated that tyrosine phosphorlylation phosphatidylinositol 3-kinase (PI3-kinase) and mitogen-activated protein kinase/extracellular-regulated kinase (ERK/MAPK) were required for internalisation of bacteria. Inhibition of Syk, a mammalian kinase, also decreased phagocytosis. JNK/SAPK did not seem to be involved in phagocytosis. The presence of protein phosphatases probably regulates phagocytosis at the intracellular level by dephosphorlyation of serine/threonine residues.

Evidence for a Role of Mitogen-Activated Protein Kinase 3/Mitogen-Activated Protein Kinase in the Development of Testicular Ischemia-Reperfusion Injury

Mitogen-activated protein kinase (MAPK) 3/MAPK1 (also known as ERK1/ERK2) plays an important role in the signal transduction pathways. To our knowledge, however, its role in the development of testicular ischemia-reperfusion injury has not yet been investigated. Therefore, we studied the pattern of MAPK3/MAPK1 activation in a experimental model of testicular ischemia-reperfusion injury. We also investigated MAPK8 to understand whether an association exists between these two MAPKs. Adult male Sprague-Dawley rats were subjected to 1 h of testicular ischemia followed by 24 h of reperfusion or to a sham testicular ischemia-reperfusion. Animals were randomized to receive PD98059, which is an inhibitor of MAPK3/MAPK1 (10 mg/kg i.p. administered immediately after detorsion), or its vehicle. The time course of MAPK3/MAPK1, MAPK8, and tumor necrosis factor (TNF; also known as TNF alpha) expression and a histological examination in both the ischemic-reperfused testis and the contralateral one were performed. In both testes, MAPK3/MAPK1 and MAPK8 expression appeared following 10 min of reperfusion and reached their highest activation after 30 min. The MAPK levels slowly decreased, and no significant expression of either kinase was observed following 2 h of reperfusion. Expression of TNF was evident after 1 h of reperfusion and reached its maximum increase after 3 h. PD98059 blunted MAPK3/MAPK1 and MAPK8, reduced TNF expression, and improved the testicular damage caused by ischemia-reperfusion injury in both testes. These data emphasize that MAPK3/MAPK1 has a role in testicular damage and that its blockade might have a future therapeutic role for the management of patients with unilateral testicular torsion.