Daniele Pietra

Design and synthesis of 2-oxindole based multi-targeted inhibitors of PDK1/Akt signaling pathway for the treatment of glioblastoma multiforme

Aggressive behavior and diffuse infiltrative growth are the main features of Glioblastoma multiforme (GBM), together with the high degree of resistance and recurrence. Evidence indicate that GBM-derived stem cells (GSCs), endowed with unlimited proliferative potential, play a critical role in tumor development and maintenance. Among the many signaling pathways involved in maintaining GSC stemness, tumorigenic potential, and anti-apoptotic properties, the PDK1/Akt pathway is a challenging target to develop new potential agents able to affect GBM resistance to chemotherapy. In an effort to find new PDK1/Akt inhibitors, we rationally designed and synthesized a small family of 2-oxindole derivatives. Among them, compound 3 inhibited PDK1 kinase and downstream effectors such as CHK1, GS3Kα and GS3Kβ, which contribute to GCS survival. Compound 3 appeared to be a good tool for studying the role of the PDK1/Akt pathway in GCS self-renewal and tumorigenicity, and might represent the starting point for the development of more potent and focused multi-target therapies for GBM.

The in vivo effect of chelidonine on the stem cell system of planarians

The presence of adult pluripotent stem cells and the amazing regenerative capabilities make planarian flatworms an extraordinary experimental model to assess in vivo the effects of substances of both natural and synthetic origin on stem cell dynamics. This study focuses on the effects of chelidonine, an alkaloid obtained from Chelidonium majus. The expression levels of molecular markers specific for stem or differentiated cells were compared in chelidonine-treated and control planarians. The use of these markers demonstrates that chelidonine produces in vivo a significant anti-proliferative effect on planarian stem cells in a dose-dependent fashion. In response to chelidonine treatment mitotic abnormalities were also observed and the number of cells able to proceed to anaphase/telophase appeared significantly reduced with respect to the controls. Our results support the possibility that chelidonine acts on cell cycle progression by inhibition of tubulin polymerization. These studies provide a basis for preclinical evaluation in vivo of the effects of chelidonine on physiologically proliferating stem cells.

Berberine exposure triggers developmental effects on planarian regeneration

The mechanisms of action underlying the pharmacological properties of the natural alkaloid berberine still need investigation. Planarian regeneration is instrumental in deciphering developmental responses following drug exposure. Here we report the effects of berberine on regeneration in the planarian Dugesia japonica. Our findings demonstrate that this compound perturbs the regenerative pattern. By real-time PCR screening for the effects of berberine exposure on gene expression, we identified alterations in the transcriptional profile of genes representative of different tissues, as well as of genes involved in extracellular matrix (ECM) remodeling. Although berberine does not influence cell proliferation/apoptosis, our experiments prove that this compound causes abnormal regeneration of the planarian visual system. Potential berberine-induced cytotoxic effects were noticed in the intestine. Although we were unable to detect abnormalities in other structures, our findings, sustained by RNAi-based investigations, support the possibility that berberine effects are critically linked to anomalous ECM remodeling in treated planarians.

Synthesis, biological assays and QSAR studies of N-(9-benzyl-2-phenyl-8-azapurin-6-yl)-amides as ligands for A1 adenosine receptors.

2-Phenyl-9-benzyl-8-azapurines, bearing at the 6 position an amido group interposed between the 8-azapurine moiety and an alkyl or a substituted phenyl group, have been synthesised and assayed as ligands for adenosine receptors. All the compounds show high affinity for the A(1) adenosine receptor, and many of them also show a good selectivity for A(1) with respect to A(2A) and A(3) adenosine receptors. Based on the quite rich library containing such compounds and relevant biological data, QSAR models, able to rationalise the results and to give a quantitative estimate of the observed trends were also developed. The obtained models can assist in the design of new compounds selectively active on A(1) adenosine receptor.

Chemical reactivity predictions: use of data mining techniques for analyzing regioselective azidolysis of epoxides.

Azidolysis of epoxides followed by reduction of the intermediate azido alcohols constitutes a valuable synthetic tool for the construction of β‐amino alcohols, an important chemical functionality occurring in many biologically active compounds of natural origin. However, depending on conditions under which the azidolysis is carried out, two regioisomeric products can be formed, as a consequence of the nucleophilic attack on both the oxirane carbon atoms. In this work, predictive models for quantitative structure‐reactivity relationships were developed by means of multiple linear regression, k‐nearest neighbor, locally weighted regression, and Gaussian Process regression algorithms. The specific nature of the problem at hand required the creation of appropriate new descriptors, able to properly reflect the most relevant features of molecular moieties directly involved in the opening process. The models so obtained are able to predict the regioselectivity of the azidolysis of epoxides promoted by sodium azide, in the presence of lithium perchlorate, on the basis of steric hindrance, and charge distribution of the substituents directly attached to the oxirane ring.

Enhancer and competitive allosteric modulation model for G-protein-coupled receptors

A new mathematical model, referred to as Enhancer and Competitive Allosteric Modulator (ECAM) model, developed with the aim of quantitatively describing the interaction of an allosteric modulator with both enhancer and competitive properties towards G-protein-coupled receptors is described here. Model simulations for equilibrium (displacement-like and saturation-like), and kinetic (association and dissociation) binding experiments were performed. The results showed the ability of the model to interpret a number of possible ligand-receptor binding behaviors. In particular, the binding properties of PD81723, an enhancer and competitive allosteric modulator for the adenosine A(1) receptor, were experimentally evaluated by radioligand binding assays and interpreted by the ECAM model. The results also offer a theoretical background enabling the design and optimization of compounds endowed with allosteric enhancer, competitive, agonist, antagonist, and inverse agonist properties.

In vitro studies of antifibrotic and cytoprotective effects elicited by proto-berberine alkaloids in human dermal fibroblasts

BACKGROUND The pathogenic mechanisms of skin fibrosis are still not completely understood, unlike the profibrotic role played by inflammatory cytokines and transforming growth factor-β1 (TGF-β1). Few antifibrotic drugs are available. Nevertheless, folk medicine suggests numerous treatments of fibrotic conditions. Based on information from folk medicine and literature, the hypothesis was made that proto-berberine alkaloids could act as antifibrotic and cytoprotective agents. METHODS The effects of berberine, dihydroberberine, canadine, stylopine, and coptisine were investigated on an in vitro model of fibrosis purposely set up. The study is based on the use of human dermal fibroblasts (HDF). The ability of the proto-berberine alkaloids investigated to modulate mitochondrial dehydrogenase activity, cell proliferation, collagen production, and inflammatory cytokine (IL-1β and IL-6) production was tested on HDF cells grown under standard growth conditions, in the presence of 100 μM H(2)O(2), simulating oxidative stress conditions, and in the presence of 34 ng/ml TGF-β1, simulating fibrotic conditions. Antiradical activity was assayed as well, as it could contribute to cytoprotection. RESULTS Each alkaloid tested showed peculiar effects on HDF. In particular, all of the alkaloids tested, with the exception of coptisine, inhibited TGF-β1-induced collagen production. CONCLUSIONS Due to its irritant effects and the lack of desired properties, coptisine has low exploitation potentialities. The other proto-berberine alkaloids investigated resulted all endowed with activities for which they can be exploited as antifibrotic and cytoprotective agents. Stylopine globally proved to be the most promising compound, being endowed with revitalizing, anti-inflammatory, antifibrotic and wound-healing promoting activities, and showing no toxic effects.

Structure-activity relationships on purine and 2,3-dihydropurine derivatives as antitubercular agents: a data mining approach.

Nowadays, many people still fall victim to tuberculosis, the disease that has a worldwide spreading. Moreover, the problem of resistance to isoniazid and rifampin, the two most effective antitubercular drugs, is assuming an ever‐growing importance. The need for new drugs active against Mycobacterium tuberculosis represents nowadays a quite relevant problem in medicinal chemistry. Several purine and 2,3‐dihydropurine derivatives have recently emerged, showing considerable antitubercular properties. In this work, a quantitative structure–activity relationship (QSAR) model was developed, which is able to predict whether new purine and 2,3‐dihydropurine derivatives belong to an ‘Active’ or ‘Inactive’ class against the above micro‐organism. The obtained prediction model is based on a classification tree; it was built with a small number of descriptors, which allowed us to outline structural features important to predict antitubercular activity of such classes of compounds.