The natural compound sanguinarine perturbs the regenerative capabilities of planarians.

The natural alkaloid sanguinarine has remarkable therapeutic properties and has been used for centuries as a folk remedy. This compound exhibits interesting anticancer properties and is currently receiving attention as a potential chemotherapeutic agent. Nevertheless, limited information exists regarding its safety for developing organisms. Planarians are an animal model known for their extraordinary stem cell-based regenerative capabilities and are increasingly used for toxicological and pharmacological studies. Here, we report that sanguinarine, at micromolar concentrations, perturbs the regeneration process in the planarian Dugesia japonica. We show that sanguinarine exposure causes defects during anterior regeneration and visual system recovery, as well as anomalous remodelling of pre-existing structures. Investigating the effects of sanguinarine on stem cells, we found that sanguinarine perturbs the transcriptional profile of early and late stem cell progeny markers. Our results indicate that sanguinarine exposure alters cell dynamics and induces apoptosis without affecting cell proliferation. Finally, sanguinarine exposure influences the expression level of H +, K+-ATPase α subunit, a gene of the P-type-ATPase pump family which plays a crucial role during anterior regeneration in planaria. On the whole, our data reveal that sanguinarine perturbs multiple mechanisms which regulate regeneration dynamics and contribute to a better understanding of the safety profile of this alkaloid in developing organisms.

Enzyme kinetics studies on 29-kDa human liver cathepsin L.

Enzyme kinetics studies reported in the literature showed that human liver Cathepsin L is active only at lysosomal acidic pH values, while biochemical studies in living cells showed that the enzyme works even at neutral pH values (in a condition compatible with the extracellular compartment). Such an apparent ambiguity highlighted the need of analysing in depth the kinetics of ~29-kDa Cathepsin L, which is the form commonly used in experiments. The stability and catalytic activity of this enzyme were investigated at different pH values, reducing and non-reducing environments, presence of copper, iron and zinc ions, and presence of the natural modulator/inhibitor cystatin B. Our experiments showed that ~29-kDa human liver Cathepsin L is stable and catalytically functional even at neutral pH values and under non-reducing conditions, which simulate the extracellular compartment. Under these conditions, Cathepsin L was also proved to interact with cystatin B, being also modulated by physiological concentrations of Cu(++) , Fe(++) and Zn(++) . This paper suppose an advance in the comprehension of the catalytic properties of human liver Cathepsin L, its implications in different physiological processes and its potential use within a drug screening programme in which agents acting extracellularly are being considered.

N-[9-(ortho-fluorobenzyl)-2-phenyl-8-azapurin-6-yl]-amides as potent and selective ligands for A1 adenosine receptors.

A series of N-[9-(ortho-fluorobenzyl)-2-phenyl-8-azapurin-6-yl]-amides were synthesized and tested for their affinity toward A1, A2A , and A3 adenosine receptor subtypes. Biological results demonstrated that the introduction of a fluorine atom at the ortho position of the 9-benzyl group generally enhanced affinity toward A1 subtype and did not significantly affect A2A and A3 affinity. Very interesting is the compound bearing a meta-fluorophenyl substituent on the carbonyl carbon of the amide group, which shows significantly high A1/A2A-A3 selectivity. Compounds of this new series, together with the previously published analogs without the fluorine atom on the 9-benzyl group, constituted the starting dataset for the development of QSAR models. The models obtained were able to rationally describe the affinity trends resulting from biological testing and to enable investigation of the role of different substituents on the 8-azapurine scaffold, as well as the influence of the newly introduced fluorine atom on the benzyl moiety. The said QSAR models can also assist in the design of new compounds selectively active on A1 adenosine receptors. Furthermore, a molecular docking study was carried out to assess hypothetical binding mode of N-[9-(ortho-fluorobenzyl)-2-phenyl-8-azapurin-6-yl]-amides to A1 adenosine receptors.

Optimizing QSAR models for predicting ligand binding to the drug-metabolizing cytochrome P450 isoenzyme CYP2D6.

The cytochrome P450 isozyme CYP2D6 binds a large variety of drugs, oxidizing many of them, and plays a crucial role in establishing in vivo drug levels, especially in multidrug regimens. The current study aimed to develop reliable predictive models for estimating the CYP2D6 inhibition properties of drug candidates. Quantitative structure-activity relationship (QSAR) studies utilizing 51 known CYP2D6 inhibitors were carried out. Performance achieved using models based on two-dimensional (2D) molecular descriptors was compared with performance using models entailing additional molecular descriptors that depend upon the three-dimensional (3D) structure of ligands. To properly compute the descriptors, all the 3D inhibitor structures were optimized such that induced-fit binding of the ligand to the active site was accommodated. CODESSA software was used to obtain equations for correlating the structural features of the ligands to their pharmacological effects on CYP2D6 (inhibition). The predictive power of all the QSAR models obtained was estimated by applying rigorous statistical criteria. To assess the robustness and predictability of the models, predictions were carried out on an additional set of known molecules (prediction set). The results showed that only models incorporating 3D descriptors in addition to 2D molecular descriptors possessed the requisite high predictive power for CYP2D6 inhibition.

Computational modeling and surface plasmon resonance analyses in the assessment of peptide ligands interacting with fibrin gamma(312-324) epitope.

Fibrin represents a suitable target for addressing delivery systems loaded by fibrinolytic drugs. Selective ligands capable to recognize fibrin could be used as targeting moieties for such systems. In this study the interactions between the gamma(312-324) epitope of human fibrin and peptidic ligands were analyzed by using experimental and computational methods. Binding free energies were calculated through the molecular mechanics/generalized born surface area approach. Good qualitative agreements between the experimental and calculated data were obtained. The binding affinity seems to be well correlated (R(2)=0.69) with the changes of the nonpolar solvation energy term computed from solvent-accessible surface area calculation. These results indicate that current methods of estimating binding free energies are efficient for achieving information on protein-ligand interactions.