Inhibition of Aedes aegypti DNA topoisomerase II by etoposide: Impact on survival and morphology of larvae and pupae.

DNA topoisomerase II enzymes maintain DNA stability during vital processes, such as genome replication, transcription and chromosomal segregation during mitosis and meiosis. In the present work, we analyzed functional aspects of the DNA topoisomerase II (AeTopII) enzyme of the mosquito Aedes aegypti. Here, we show that AeTopII mRNA is expressed at all stages of mosquito development. By in situ hybridization, we found that the AeTopII mRNA is concentrated along the ovarian follicular cells as well as in the region of the follicles. The observed expression profiles likely reflect increased topoisomerase II cellular requirements due to the intense ovarian growth and egg production following blood feeding in Ae. aegypti females. The drug etoposide, a classic inhibitor of topoisomerase II, was used for in vivo testing with 2nd stage larvae, in order to investigate the functional importance of this enzyme in Ae. aegypti survival and development. Inhibition of topoisomerase II activity with etoposide concentrations ranging from 10 to 200 µM did not leads to the immediate death of larvae. However, after 10 days of observation, etoposide treatments resulted in 30-40% decrease in survival, in a dose dependent manner, with persisting larvae and pupae presenting incomplete development, as well as morphological abnormalities. Also, approximately 50% of the treated larvae did not reach the pupal stage. Thus, we conclude that AeTopII is a vital enzyme in the development of Ae. aegypti and its sensitivity to inhibitors should be explored for potential chemical agents to be used in vector control.

The effects of Roundup® in embryo development and energy metabolism of the zebrafish (Danio rerio).

Roundup® is currently the most widely used and sold agricultural pesticide in the world. The objective of this work was to investigate the effects of Roundup® on energy metabolism during zebrafish (Danio rerio) embryogenesis. The embryo toxicity test was performed for 96 h post-fertilisation and the sublethal concentration of Roundup® was defined as 58.3 mg/L, which resulted in failure to inflate the swim bladder. Biochemical assays were performed with viable embryos following glyphosate exposure, and no significant effects on protein, glucose, glycogen, triglyceride levels or the enzymatic activities of alanine aminotransferase and aspartate aminotransferase were observed. However, the activity of hexokinase was significantly altered following exposure to 11.7 mg/L Roundup®. Through molecular docking we have shown for the first time that the interactions of glucokinase and hexokinases 1 and 2 with glyphosate showed significant interactions in the active sites, corroborating the biochemical results of hexokinase activity in zebrafish exposed to the chemical. From the results of molecular docking interactions carried out on the Zfishglucok, ZfishHK1 and ZfishHK2 models with the glyphosate linker, it can be concluded that there are significant interactions between glyphosate and active sites of glucokinase and hexokinase 1 and 2 proteins. The present work suggests that Roundup® can induce problems in fish embryogenesis relating to the incapacity of swim bladder to inflate. This represents the first study demonstrating the interaction of glyphosate with hexokinase and its isoforms.

Proposed anti-HSV compounds isolated from Simira species.

Secondary metabolites isolated from Simira eleiezeriana and Simira glaziovii were evaluated against herpes simplex virus (HSV-1) and (HSV-2). The 50% effective concentrations values (EC50) were calculated from the dose-response curve and the selectivity index (SI) against the virus. The physicochemical data LogP, (PSA), (NRB), (HBA) and (HBD) were obtained using Marvin Sketch. Among the tested compounds, conipheraldeyde, harman and simirane A showed better results with EC50 6.39; 4.90; 4.61 µg/mL and SI 78.3; 11.8; 7.01, respectively, for HSV-1, and EC50 41.2; 71.8; 3.73 µg/mL and SI 12.1; 24.7; 8.7, respectively, for HSV-2. The percentage of inhibition (PI) obtained for HSV-1 were higher than 60%, and for HSV-2 these compounds showed PI > 90%. The physical chemical data showed that the most active compounds satisfy the attributes for drugs with good oral bioavailability.

Molecular and structural characterization of novel cystatins from the taiga tick Ixodes persulcatus.

Cystatins are cysteine peptidase inhibitors that in ticks mediate processes such as blood feeding and digestion. The ixodid tick Ixodes persulcatus is endemic to the Eurasia, where it is the principal vector of Lyme borreliosis. To date, no I. persulcatus cystatin has been characterized. In the present work, we describe three novel cystatins from I. persulcatus, named JpIpcys2a, JpIpcys2b and JpIpcys2c. In addition, the potential of tick cystatins as cross-protective antigens was evaluated by vaccination of hamsters using BrBmcys2c, a cystatin from Rhipicephalus microplus, against I. persulcatus infestation. Sequence analysis showed that motifs that are characteristic of cystatins type 2 are fully conserved in JpIpcys2b, while mutations are present in both JpIpcys2a and JpIpcys2c. Protein-protein docking simulations further revealed that JpIpcys2a, JpIpcys2b and JpIpcys2c showed conserved binding sites to human cathepsins L, all of them covering the active site cleft. Cystatin transcripts were detected in different I. persulcatus tissues and instars, showing their ubiquitous expression during I. persulcatus development. Serological analysis showed that although hamsters immunized with BrBmcys2c developed a humoral immune response, this response was not adequate to protect against a heterologous challenge with I. persulcatus adult ticks. The lack of cross-protection provided by BrBmcys2c immunization is perhaps linked to the fact that cystatins cluster into multigene protein families that are expressed differentially and exhibit functional redundancy. How to target such small proteins that are secreted in low quantities remains a challenge in the development of suitable anti-tick vaccine antigens.

Synthesis, Biological Evaluation and Molecular Docking of New Benzenesulfonylhydrazone as Potential anti-Trypanosoma cruzi Agents.

BACKGROUND: Chagas disease is a public health problem caused by Trypanosoma cruzi. Cruzain is a pharmacological target for designing a new drug against this parasite. Hydrazone and Nacylhydrazone derivatives have been traditionally associated as potential Cruzain inhibitors. Additionally, benzenesulfonyl derivatives show trypanocidal activity. Therefore, in this study, the combination of both structures has been taken into account for drug design. METHODS: Seven benzenesulfonylhydrazone (BS-H) and seven N-propionyl benzenesulfonylhydrazone (BS-NAH) derivatives were synthetized and elucidated by infrared spectroscopy, nuclear magnetic resonance, and elemental analysis. All compounds were evaluated biologically in vitro against two strains of Trypanosoma cruzi (NINOA and INC-5), which are endemic in Mexico, and compared with the reference drugs nifurtimox and benznidazole. In order to gain insight into the putative molecular origin of the trypanocidal properties of these derivatives, docking studies were carried out with Cruzain. RESULTS: Compounds 4 and 6 (BS-H) and 10, 12-14 (BS-NAH) showed the best biological activity against NINOA and INC-5 strains, respectively. Compound 13 was the most potent trypanocidal compound showing a LC50 of 0.06 µM against INC-5 strain. However, compound 4 showed the best activity against both strains (LC50 <30 µM). Theoretical binding modes obtained suggested covalent binding that could explain their biological activity. CONCLUSION: Benzenesulfonyl and N-propionyl benzenesulfonyl hydrazone derivatives are good options for developing new trypanocidal agents. Particularly, compound 4 could be considered a lead compound.

A novel mechanism of functional cooperativity regulation by thiol redox status in a dimeric inorganic pyrophosphatase.

BACKGROUND: Inorganic PPases are essential metal-dependent enzymes that convert pyrophosphate into orthophosphate. This reaction is quite exergonic and provides a thermodynamic advantage for many ATP-driven biosynthetic reactions. We have previously demonstrated that cytosolic PPase from R. microplus embryos is an atypical Family I PPase. Here, we explored the functional role of the cysteine residues located at the homodimer interface, its redox sensitivity, as well as structural and kinetic parameters related to thiol redox status. METHODS: In this work, we used prokaryotic expression system for recombinant protein overexpression, biochemical approaches to assess kinetic parameters, ticks embryos and computational approaches to analyze and predict critical amino acids as well as physicochemical properties at the homodimer interface. RESULTS: Cysteine 339, located at the homodimer interface, was found to play an important role in stabilizing a functional cooperativity between the two catalytic sites, as indicated by kinetics and Hill coefficient analyses of the WT-rBmPPase. WT-rBmPPase activity was up-regulated by physiological antioxidant molecules such as reduced glutathione and ascorbic acid. On the other hand, hydrogen peroxide at physiological concentrations decreased the affinity of WT-rBmPPase for its substrate (PPi), probably by inducing disulfide bridge formation. CONCLUSIONS: Our results provide a new angle in understanding redox control by disulfide bonds formation in enzymes from hematophagous arthropods. The reversibility of the down-regulation is dependent on hydrophobic interactions at the dimer interface. GENERAL SIGNIFICANCE: This study is the first report on a soluble PPase where dimeric cooperativity is regulated by a redox mechanism, according to cysteine redox status.

Cardanol-derived AChE inhibitors: Towards the development of dual binding derivatives for Alzheimer's disease.

Cardanol is a phenolic lipid component of cashew nut shell liquid (CNSL), obtained as the byproduct of cashew nut food processing. Being a waste product, it has attracted much attention as a precursor for the production of high-value chemicals, including drugs. On the basis of these findings and in connection with our previous studies on cardanol derivatives as acetylcholinesterase (AChE) inhibitors, we designed a novel series of analogues by including a protonable amino moiety belonging to different systems. Properly addressed docking studies suggested that the proposed structural modifications would allow the new molecules to interact with both the catalytic active site (CAS) and the peripheral anionic site (PAS) of AChE, thus being able to act as dual binding inhibitors. To disclose whether the new molecules showed the desired profile, they were first tested for their cholinesterase inhibitory activity towards EeAChE and eqBuChE. Compound 26, bearing an N-ethyl-N-(2-methoxybenzyl)amine moiety, showed the highest inhibitory activity against EeAChE, with a promising IC50 of 6.6 µM, and a similar inhibition profile of the human isoform (IC50 = 5.7 µM). As another positive feature, most of the derivatives did not show appreciable toxicity against HT-29 cells, up to a concentration of 100 µM, which indicates drug-conform behavior. Also, compound 26 is capable of crossing the blood-brain barrier (BBB), as predicted by a PAMPA-BBB assay. Collectively, the data suggest that the approach to obtain potential anti-Alzheimer drugs from CNSL is worth of further pursuit and development.

Synthesis and Biological Evaluation of Pyrazolo[3,4-b]pyridin-4-ones as a New Class of Topoisomerase II Inhibitors.

A series of 1,3,6-triphenylpyrazolo[3,4-b]pyridin-4-one derivatives was designed, synthesized and evaluated for cytotoxic activity in A375 human melanoma and human erythroleukemia (HEL) cells. The new pyrazolopyridones displayed comparable activities to the antitumor compound etoposide. The inhibitory effect of compounds 17, 18, 27 and 32 against topoisomerase II-mediated cleavage activities was measured finding good correlation with the results obtained from MTS assay. Docking studies into bacterial topoisomerase II (DNA Gyrase), topoisomerase IIα and topoisomerase IIß binding sites in the DNA binding interface were performed.

Synthesis of novel 2,3,4-trisubstituted-oxazolidine derivatives and in vitro cytotoxic evaluation.

We have previously reported the discovery of cytotoxic and pro-apoptotic hit compound 1,1-dimethylethyl (S)- 2,2-dimethyl-4-[(3-nitrophenoxy)methyl]-3-oxazolidinecarboxylate 1 against leukemia cells. In the present work we describe the synthesis of 25 derivatives of this hit varying the substituent at ring or stereochemistry of the oxazolidine ring and evaluated them against human cancer cells lines. Six compounds exerted significant activity against HL60 promyelocytic leukemia cells with IC50 in low micromolar range (4-18 µM) and three compounds displayed activity against MDA-MB231 breast cancer cells (25-37 µM). In vitro cytotoxicity on normal cells PBMC (human peripheral blood mononuclear cells) was also evaluated. Compounds 7e (p-NO2, S) and 7m (p-COOCH3, S) showed good antiproliferative activity against HL60 (4 and 5 µM) and MDA-MB231 (37 and 25 µM) without affecting lymphocyte proliferation in PBMC, indicating low toxicity to normal cells. Besides, compound 7e induced DNA fragmentation on about 100% of HL60 cells at 50 µM. In this case, it was more potent than 7m and lead 1. This indicated that compound 7e has a great pro-apoptotic potential.

Identification and structural-functional analysis of cyclin-dependent kinases of the cattle tick Rhipicephalus (Boophilus) microplus.

Cyclin-dependent kinases (CDKs) are a family of serine/threonine kinases essential for cell cycle progression. Herein, we describe the participation of CDKs in the physiology of Rhipicephalus microplus, the southern cattle tick and an important disease vector. Firstly, amino acid sequences homologous with CDKs of other organisms were identified from a R. microplus transcriptome database in silico. The analysis of the deduced amino acid sequences of CDK1 and CDK10 from R. microplus showed that both have caspase-3/7 cleavage motifs despite their differences in motif position and length of encoded proteins. CDK1 has two motifs (DKRGD and SAKDA) located opposite to the ATP binding site while CDK10 has only one motif (SLLDN) for caspase 3-7 near the ATP binding site. Roscovitine (Rosco), a purine derivative that inhibits CDK/cyclin complexes by binding to the catalytic domain of the CDK molecule at the ATP binding site, which prevents the transfer of ATP's γphosphoryl group to the substrate. To determine the effect of Rosco on tick CDKs, BME26 cells derived from R. microplus embryo cells were utilized in vitro inhibition assays. Cell viability decreased in the Rosco-treated groups after 24 hours of incubation in a concentration-dependent manner and this was observed up to 48 hours following incubation. To our knowledge, this is the first report on characterization of a cell cycle protein in arachnids, and the sensitivity of BME26 tick cell line to Rosco treatment suggests that CDKs are potential targets for novel drug design to control tick infestation.

Docking, synthesis and anti-diabetic activity of novel sulfonylhydrazone derivatives designed as PPAR-gamma agonists.

Diabetes is a metabolic disorder characterized by hyperglycemia. When not properly controlled, complications include neuropathy, coronary artery disease, and renal failure. Several drugs are approved for diabetes treatment; however their use is associated with side effects and lack of efficacy in attenuating the development of long-term complications. This work describes the virtual screening and synthesis of a novel series of sulfonylhydrazone derivatives designed as peroxisome proliferator-activated receptor gamma (PPARγ) agonists and investigation of the analogs for hypoglycemic activity in a murine model of diabetes. Docking studies identified LASSBio-331 (5) as having theoretical affinity for PPARγ similar to the prototype (S)-rosiglitazone. Several structural modifications were proposed for the structure of LASSBio-331, resulting in the synthesis of five novel compounds, which showed experimental affinity for PPARγ. Among these new compounds, LASSBio-1471 (15) had the best theoretical binding energy for PPARγ and was selected for testing in STZ-induced diabetes. Four weeks after single intravenous injection of STZ (60 mg/kg), Wistar rats were treated with vehicle (DMSO) or LASSBio-1471 (20 mg/kg, i.p.) for 7 days. The blood glucose levels of rats treated with LASSBio-1471 were reduced from 548.4 ± 26.0 mg/dL before treatment to 259.6 ± 73.1 mg/dL (P < 0.05). Paw withdrawal threshold was significantly reduced in diabetic rats and was restored from 21.9 ± 1.7 g to 36.7 ± 1.2 g after 7 days of treatment with LASSBio-1471 (P < 0.05). Thus, the novel sulfonylhydrazone derivative is a PPARγ ligand that is effective for treatment of diabetic neuropathy in STZ-injected rats.

Design, synthesis, and pharmacological evaluation of N-acylhydrazones and novel conformationally constrained compounds as selective and potent orally active phosphodiesterase-4 inhibitors.

Among a small series of tested N-acylhydrazones (NAHs), the compound 8a was selected as a selective submicromolar phosphodiesterase-4 (PDE4) inhibitor associated with anti-TNF-α properties measured both in vitro and in vivo. The recognition pattern of compound 8a was elucidated through molecular modeling studies based on the knowledge of the 3D-structure of zardaverine, a PDE4 inhibitor resembling the structure of 8a, cocrystallized with the PDE4. Based on further conformational analysis dealing with N-methyl-NAHs, a quinazoline derivative (19) was designed as a conformationally constrained NAH analogue and showed similar in vitro pharmacological profile, compared with 8a. In addition 19 was found active when tested orally in LPS-evoked airway hyperreactivity and fully confirmed the working hypothesis supporting this work.

Synthesis and characterization of the atropisomeric relationships of a substituted N-phenyl-bipyrazole derivative with anti-inflammatory properties.

This work describes the atropisomeric relationships of 3-methyl-5-(3-methyl-5-phenyl-1H-pyrazol-1-yl)-1-phenyl-1H-pyrazol-4-amine (2d), which belongs to series 4-aminobipyrazole derivatives designed as anti-inflammatory agents. The (1)H nuclear magnetic resonance spectra obtained in the presence of a chiral lanthanide shift salt associated to chiral high-performance liquid chromatography analysis, X-ray diffraction, and molecular modeling tools confirmed that ortho bis-functionalized bipyrazole 2d exists as a mixture of aR,aS-atropisomers. These results provide useful information to understand the pharmacological profile of this derivative and of other 4-aminobipyrazole analogs.

Structure-based design and biological profile of (E)-N-(4-Nitrobenzylidene)-2-naphthohydrazide, a novel small molecule inhibitor of IκB kinase-ß.

In this study, we describe the rational design, molecular modeling and pharmacological profile of a novel IKK-ß inhibitor (E)-N-(4-nitrobenzylidene)-2-naphthohydrazide (LASSBio-1524). The design based on the IKK-ß active site, and a privileged structure template yielded a novel IKK-ß inhibitor scaffold with significant selectivity over IKK-α and CHK2, as assessed by an in vitro kinase assay. For a better understanding of the structural requirements of IKK-ß inhibition, molecular dynamics simulations of LASSBio-1524 (3) were performed. The NAH derivative LASSBio-1524 (3), was able to suppress arachidonic acid-induced edema formation in a dose-dependent manner, demonstrating an in vivo anti-inflammatory effect. The molecular architecture of this novel, low-molecular weight IKK-ß inhibitor is encouraging for further lead optimization toward the development of innovative anti-inflammatory drug candidates.

2-Acetylpyridine thiosemicarbazones: cytotoxic activity in nanomolar doses against malignant gliomas.

2-acetylpyridine N(4)-phenyl thiosemicarbazone (H2Ac4Ph), and its N(4)-ortho-tolyl (H2Ac4oT), N(4)-meta-tolyl (H2Ac4mT), N(4)-para-tolyl (H2Ac4pT), N(4)-ortho-chlorophenyl (H2Ac4oClPh), N(4)-meta-chlorophenyl (H2Ac4mClPh) and N(4)-para-chlorophenyl (H2Ac4pClPh) derivatives were assayed for their cytotoxicity against RT2 (expressing p53 protein) and against T98 (expressing mutant p53 protein) glioma cells. The compounds were highly cytotoxic against RT2 (IC50=24-1.4 nM) and T98 cells (IC50=50-1.0 nM). IC50 for cisplatin=5 (RT2) and 17 µM (T98). The thiosemicarbazones presented haemolytic activity with IC50>10(-3)M, indicating a very good therapeutic index. SAR studies suggested that stereo properties are critical to define the potential activity of the studied compounds against the RT2 cell line, while electronic properties seem to be important for interaction with the biological target in T98 cells.

Structural insights into IKKbeta inhibition by natural products staurosporine and quercetin.

This Letter describes the results of two combined approaches: homology modeling and molecular docking studies, in order to propose the molecular basis of IKKbeta inhibition by staurosporine and quercetin as ATP-competitive inhibitors. The results provides a rationale and structural frameworks for designing potent ATP binding-site inhibitors of IKKbeta, which is an attractive drug target for inflammatory diseases and has been found to be responsible for some of the already observed pharmacological effects for marketed drugs.

Development of CoMFA and CoMSIA models of affinity and selectivity for indole ligands of cannabinoid CB1 and CB2 receptors.

This paper describes CoMFA and CoMSIA studies for affinity and selectivity of a series of indole ligands to cannabinoid CB1 and CB2 receptors. The developed models have proven to be predictive, with average q(2) of 0.675 and average r(2) of 0.855, demonstrating a good statistical validation. The obtained results have helped us to understand the structural motifs that are responsible for the affinity and selectivity of some of these derivatives towards each subtype of cannabinoid receptor and have demonstrated that the exploited 3D-QSAR methods could be useful tools for the design of new safer analogues presenting better affinity and selectivity profiles.

Synthesis, pharmacological evaluation and docking studies of new sulindac analogues.

This paper describes the synthesis, pharmacological evaluation and docking studies of a series of new sulindac analogues. Overall, the designed compounds revealed good, in vivo, antinociceptive activity and satisfactory anti-inflammatory profile. Flexible molecular docking with COX-1/COX-2 has shown putative binding modes of the designed compounds while the theoretical evaluation of cell permeability based on Lipinski's rule of five has helped rationalize the biological results.

Novel 6-methanesulfonamide-3,4-methylenedioxyphenyl-N-acylhydrazones: orally effective anti-inflammatory drug candidates.

We described herein the molecular design of novel in vivo anti-inflammatory 6-methanesulfonamide-3,4-methylenedioxyphenyl-N-acylhydrazone derivatives (1) planned by applying the molecular hybridization approach. This work also points out to the discovery of LASSBio-930 (1c) as a novel anti-inflammatory and anti-hyperalgesic prototype, which was able to reduce carrageenan-induced rat paw edema with an ED(50) of 97.8 micromol/kg, acting mainly as a non-selective COX inhibitor.

Synthesis, trypanocidal activity and docking studies of novel quinoxaline-N-acylhydrazones, designed as cruzain inhibitors candidates.

In this paper, we report the structural design, synthesis, trypanocidal activity and docking studies of novel quinoxaline-N-acylhydrazone (NAH) derivatives, planned as cruzain inhibitors candidates, a cysteine protease essential for the survival of Trypanosoma cruzi within the host cell. The salicylaldehyde N-acylhydrazones 7a and 8a presented IC(50) values of the same magnitude order than the standard drug nifurtimox (Nfx), when tested in vitro against epimastigote forms of Trypanosoma cruzi (Tulahuen 2 strain) and were non-toxic at the highest assayed doses rendering selectivity indexes (IC(50) (macrophages)/IC(50) (Trypanosoma cruzi)) of >25 for 7a and >20 for 8a, with IC(50) values in macrophages >400 microM.