Biomedical subjects

Giuseppe Zagotto

Publications and source records attributed to Giuseppe Zagotto.

13 recordsLinked to original sources

PubMed2007

Tetrabromocinnamic acid (TBCA) and related compounds represent a new class of specific protein kinase CK2 inhibitors.

Abnormally high constitutive activity of protein kinase CK2, levels of which are elevated in a variety of tumours, is suspected to underlie its pathogenic potential. The most widely employed CK2 inhibitor is 4,5,6,7-tetrabromobenzotriazole (TBB), which exhibits a comparable efficacy toward another kinase, DYRK1 a. Here we describe the development of a new class of CK2 inhibitors, conceptually derived from TBB, which have lost their potency toward DYRK1 a. In particular, tetrabromocinnamic acid (TBCA) inhibits CK2 five times more efficiently than TBB (IC50 values 0.11 and 0.56 microM, respectively), without having any comparable effect on DYRK1 a (IC50 24.5 microM) or on a panel of 28 protein kinases. The usefulness of TBCA for cellular studies has been validated by showing that it reduces the viability of Jurkat cells more efficiently than TBB through enhancement of apoptosis. Collectively taken, the reported data support the view that suitably derivatized tetrabromobenzene molecules may provide powerful reagents for dissecting the cellular functions of CK2 and counteracting its pathogenic potentials.

Adenosine Triphosphate↗

PubMed2006

Identification of ellagic acid as potent inhibitor of protein kinase CK2: a successful example of a virtual screening application.

Casein kinase 2 (CK2) is a ubiquitous, essential, and highly pleiotropic protein kinase whose abnormally high constitutive activity is suspected to underlie its pathogenic potential in neoplasia and other diseases. Using a virtual screening approach, we have identified the ellagic acid, a naturally occurring tannic acid derivative, as a novel potent CK2 inhibitor. At present, ellagic acid represents the most potent known CK2 inhibitor (K(i) = 20 nM).

Binding Sites↗

PubMed2006

A QSAR model for in silico screening of MAO-A inhibitors. Prediction, synthesis, and biological assay of novel coumarins.

This work explores the potential of the MARCH-INSIDE methodology to seek a QSAR for MAO-A inhibitors from a heterogeneous series of compounds. A Markov model was used to quickly calculate the molecular electron delocalization, polarizability, refractivity, and n-octanol/water partition coefficients for a series of 1406 active/nonactive compounds. LDA was subsequently used to fit a classification function. The model showed 92.8% and 91.8% global accuracy and predictability in training and validation studies. This QSAR model was validated through a virtual screening of a series of coumarin derivatives. The 15 selected compounds were prepared and evaluated as in vitro MAO-A inhibitors. The theoretical prediction was compared with the experimental results and the model correctly predicted 13 compounds with only two mistakes on compounds with activities very close to the cutoff point established for the model. Consequently, this method represents a useful tool for the "in silico" screening of MAO-A inhibitors.

Algorithms↗

PubMed2006

The scent of urine spots of male mice, Mus musculus: Changes in chemical composition over time.

A dominant male mouse scent-marks his territory very frequently by emitting small urinary spots. The urine spots release in the air a variety of odorants that transmit different information to other mice, especially those concerning the time of deposition. To investigate this effect, small spots of urine of a dominant male mouse were left to freely release the odorants in the air for time intervals ranging from 0 min to 24 h prior to sampling. Thereupon, the odorants remaining in the spot were sampled at diffusion equilibrium (45 degrees C) in a small vial by means of headspace solid-phase microextraction followed by gas chromatography coupled to flame ionisation detection and mass spectrometry. Thirteen odorants were consistently found. Nine odorants were identified and four were matched. The rate of release of each odorant was characteristic and was described using principal component analysis. A first principal component was based on nine early odorants that showed a decreasing release over time. The odorants were 2,4-dehydro-exo-brevicomin, an unknown with 78% matching to 4-acetonilcycloheptanone, linalool, 2,4-dimethyl-phenol, 4-ethylphenol, indole, 2-butyl-1-octanol, an unknown with 83% matching to 2-ethyl-1-decanol, and 2,4-bis-(1,1-dimethylethyl)phenol. A second principal component, based on two unknowns with 73% matching to yohimban-17-one and 71% matching to the 2-methyl-3-hydroxy-2,4,4-trimethyl ester of propanoic acid, had an irregular release after deposition. A third principal component of late odorants, based on 2-sec-butyl-4,5-dihydrothiazole and 6,10-dimethyl-5,9-undecaden-2-one, had a peak of release at about 22 min. In conclusion, the release of the odorants in the headspace of a urine spot may code and transmit information on the deposition time.

Animals↗

PubMed2005

New water soluble pyrroloquinoline derivatives as new potential anticancer agents.

A new class of water soluble 3H-pyrrolo[3,2-f]quinoline derivatives has been synthesized and investigated as potential anticancer drugs. Water solubility profiles have been used to select the most promising derivatives. The novel compound 10, having two (2-diethylamino-ethyl) side chains linked through positions 3N and 9O, presents a suitable water solubility profile, and it was shown to exhibit cell growth inhibitory properties when tested against the in-house panel of cell lines, in particular those obtained from melanoma.

Antineoplastic Agents↗

PubMed2004

Inhibition of protein kinase CK2 by condensed polyphenolic derivatives. An in vitro and in vivo study.

ATP site-directed inhibitors that can target individual kinases are powerful tools for use in signal transduction research, all the more so in the case of a pleiotropic, constitutively active protein kinase such as CK2, which is not turned on in response to specific stimuli. By screening a library of more than 200 derivatives of natural polyphenolic compounds, we have identified 16 molecules which inhibit CK2 with IC(50) values of <or=1 microM. They belong to the classes of anthraquinones (six compounds), xanthenones (two compounds), fluorenones (one compound), and coumarins (seven compounds), and their inhibitory potency correlates with the presence of nitro, amino, or halogen substituents at specific positions. Three of the most potent inhibitors, MNX (1,8-dihydroxy-4-nitroxanthen-9-one), NBC (8-hydroxy-4-methyl-9-nitrobenzo[g]chromen-2-one), and DBC (3,8-dibromo-7-hydroxy-4-methylchromen-2-one), whose IC(50) values range between 0.13 and 0.36 microM, are quite specific toward CK2 within a panel of 33 protein kinases tested. Treatment of Jurkat cells with these compounds promotes inhibition of endogenous CK2 and induction of apoptosis. A correlation is observed between their efficacy as CK2 inhibitors (as judged from IC(50) values) and their capacity to induce cell death (DC(50) values). Mutations of the unique CK2alpha residues Val66 and/or Ile174 to alanine have a detrimental effect on inhibition by these compounds with 16-67-fold increases in IC(50) values. The combined usage of these reagents can be exploited to gain information about cellular functions mediated by CK2.

Apoptosis↗

PubMed2004

Toward efficient Zn(II)-based artificial nucleases.

A series of cis-cis-triaminocyclohexane Zn(II) complex-anthraquinone intercalator conjugates, designed in such a way to allow their easy synthesis and modification, have been investigated as hydrolytic cleaving agents for plasmid DNA. The ligand structure comprises a triaminocyclohexane platform linked by means of alkyl spacers of different length (from C(4) to C(8)) to the anthraquinone group which may intercalate the DNA. At a concentration of 5 microM, the complex of the derivative with a C(8) alkyl spacer induces the hydrolytic stand scission of supercoiled DNA with a rate of 4.6 x 10(-6) s(-1) at pH 7 and 37 degrees C. The conjugation of the metal complex with the anthraquinone group leads to a 15-fold increase of the cleavage efficiency when compared with the anthraquinone lacking Zn-triaminocyclohexane complex. The straightforward synthetic procedure employed, allowing a systematic change of the spacer length, made possible to gain more insight on the role of the intercalating group in determining the reactivity of the systems. Comparison of the reactivity of the different complexes shows a remarkable increase of the DNA cleaving efficiency with the length of the spacer. In the case of too-short spacers, the advantages due to the increased DNA affinity are canceled due to the incorrect positioning of the reactive group, thus leading to cleavage inhibition.

Anthraquinones↗

PubMed2004

Development of DNA topoisomerase-related therapeutics: a short perspective of new challenges.

Antitumor agents targeting DNA and DNA-associated processes are widely used in the treatment of human cancers and produce significant increases in the survival of patients. DNA topoisomerases remain the most significant target of these cytotoxic drugs and constitute a growing family of nuclear enzymes that regulate DNA topology during DNA replication and recombination, DNA transcription, chromosome condensation-decondensation and segregation. Major progress has been attained in recent years in the understanding of the structures of these enzymes and their main cellular functions, hopefully providing new opportunities for pharmacological interventions. New leads and derivatives of known structures have been reported recently, and here they will be discussed highlighting the challenges to find innovative and more effective drugs. Moreover, we will review novel and diverse approaches relevant to the development of new topoisomerase-related therapeutics.

Animals↗

PubMed2003

Some biochemical properties of melatonin and the characterization of a relevant metabolite arising from its interaction with H2O2.

Melatonin is an efficient protector against hydrogen peroxide(H2O2)-induced lipid peroxidation and acts in a concentration-dependent manner. Hydrogen peroxide is rather a water stable molecule which is able to cross the cell membrane much better than some important free radicals such as superoxide anion, and consequently its local production can lead to significant spread by diffusion. In this paper we report data regarding some biochemical properties of melatonin as well as the chemical characterization of the major product formed from the interaction between melatonin and H2O2 (N1-acetyl-N2-formyl-5-methoxykynuramine) that are consistent with previous data reported by other authors. The effect of melatonin on catalase, glutathione peroxidase and superoxide dismutase in in vitro and in vivo experiments is also reported.

Animals↗

PubMed2003

Absolute configuration of 2-sec-butyl-4,5-dihydrothiazole in male mouse urine.

The absolute configuration of 2-sec-butyl-4,5-dihydrothiazole (DHT) in urine of adult male mice was determined through chiral trifluoroacetyl derivative capillary chromatography by comparing the retention time with synthetic standards. (S)-DHT was extracted from fresh urine, while neither (R)-DHT nor the racemization of (S)-DHT were detected. We can conclude that DHT in urine possesses the S configuration, although we cannot exclude a minor component in the R configuration. (S)-DHT was then characterized for binding to the complex of major urinary proteins of male mouse urine (MUP) and for a behavioral response, the competitive scent marking behavior (countermarking). The binding constant of (S)-DHT to MUP (determined by competitive displacement) was 8.2 +/- 0.6 microM (mean +/- SD) and was 10.5 +/- 0.6 microM for R-DHT, thus excluding a relevant difference in binding. (S)-DHT modified countermarking in a peculiar way. Male mice were slow in countermarking urinary spots streaked 2 days earlier and on top of which (S)-DHT was added shortly before the test. This response was not seen when adding (S)-DHT to freshly streaked urinary spots or to clean paper. Unlike (S)-DHT, (R)-DHT prompted countermarking rather than delaying it. We can further conclude that (S)-DHT in male mouse urine is an aversive chemosignal for countermarking.

Animals↗

PubMed2002

Inhibition of protein kinase CK2 by anthraquinone-related compounds. A structural insight.

Protein kinases play key roles in signal transduction and therefore are among the most attractive targets for drug design. The pharmacological aptitude of protein kinase inhibitors is highlighted by the observation that various diseases with special reference to cancer are because of the abnormal expression/activity of individual kinases. The resolution of the three-dimensional structure of the target kinase in complex with inhibitors is often the starting point for the rational design of this kind of drugs, some of which are already in advanced clinical trial or even in clinical practice. Here we present and discuss three new crystal structures of ATP site-directed inhibitors in complex with "casein kinase-2" (CK2), a constitutively active protein kinase implicated in a variety of cellular functions and misfunctions. With the help of theoretical calculations, we disclose some key features underlying the inhibitory efficiency of anthraquinone derivatives, outlining three different binding modes into the active site. In particular, we show that a nitro group in a hydroxyanthraquinone scaffold decreases the inhibitory constants K(i) because of electron-withdrawing and resonance effects that enhance the polarization of hydroxylic substituents in paraposition.

Anthraquinones↗

PubMed2002

Sequence-specific interactions of drugs interfering with the topoisomerase-DNA cleavage complex.

DNA-processing enzymes, such as the topoisomerases (tops), represent major targets for potent anticancer (and antibacterial) agents. The drugs kill cells by poisoning the enzymes' catalytic cycle. Understanding the molecular details of top poisoning is a fundamental requisite for the rational development of novel, more effective antineoplastic drugs. In this connection, sequence-specific recognition of the top-DNA complex is a key step to preferentially direct the action of the drugs onto selected genomic sequences. In fact, the (reversible) interference of drugs with the top-DNA complex exhibits well-defined preferences for DNA bases in the proximity of the cleavage site, each drug showing peculiarities connected to its structural features. A second level of selectivity can be observed when chemically reactive groups are present in the structure of the top-directed drug. In this case, the enzyme recognizes or generates a unique site for covalent drug-DNA binding. This will further subtly modulate the drug's efficiency in stimulating DNA damage at selected sites. Finally, drugs can discriminate not only among different types of tops, but also among different isoenzymes, providing an additional level of specific selection. Once the molecular basis for DNA sequence-dependent recognition has been established, the above-mentioned modes to generate selectivity in drug poisoning can be rationally exploited, alone or in combination, to develop tailor-made drugs targeted at defined loci in cancer cells.

Animals↗

PubMedDate not supplied

Toward the rational design of protein kinase casein kinase-2 inhibitors.

Casein kinase-2 (CK2) probably is the most pleiotropic member of the protein kinase family, with more than 200 substrates known to date. Unlike the great majority of protein kinases, which are tightly regulated enzymes, CK2 is endowed with high constitutive activity, a feature that is suspected to underlie its oncogenic potential and possible implication in viral infections. This makes CK2 an attractive target for anti-neoplastic and antiviral drugs. Here, we present an overview of our present knowledge about CK2 inhibitors, with special reference to the information drawn from two recently solved crystal structures of CK2alpha in complex with emodin and with 4,5,6,7-tetrabromo-2-azabenzimidazole (TBB), this latter being the most specific CK2 inhibitor known to date. A comparison with a series of anthraquinone and xanthenone derivatives highlights the crucial relevance of the hydroxyl group at position 3 for inhibition by emodin, and discloses the possibility of increasing the inhibitory potency by placing an electron withdrawing group at position 5. We also present mutational data corroborating the relevance of two hydrophobic residues unique to CK2, Val66 and Ile174, for the interactions with emodin and TBB, but not with the flavonoid inhibitors quercetin and fisetin. In particular, the CK2alpha mutant V66A displays 27- and 11-fold higher IC(50) values with emodin and TBB, respectively, as compared with the wild-type, while the IC(50) value with quercetin is unchanged. The data presented pave the road toward the rational design of more potent and selective inhibitors of CK2 and the generation of CK2 mutants refractory to inhibition, useful to probe the implication of CK2 in specific cellular functions.

Animals↗