Giuseppina Ferrara

Functional Cross Talk between CXCR4 and PDGFR on Glioblastoma Cells Is Essential for Migration

Glioblastoma (GBM) is the most common and aggressive form of brain tumor, characterized by high migratory behavior and infiltration in brain parenchyma which render classic therapeutic approach ineffective. The migratory behaviour of GBM cells could be conditioned by a number of tissue- and glioma-derived cytokines and growth factors. Although the pro-migratory action of CXCL12 on GBM cells in vitro and in vivo is recognized, the molecular mechanisms involved are not clearly identified. In fact the signaling pathways involved in the pro-migratory action of CXCL12 may differ in individual glioblastoma and integrate with those resulting from abnormal expression and activation of growth factor receptors. In this study we investigated whether some of the receptor tyrosine kinases commonly expressed in GBM cells could cooperate with CXCL12/CXCR4 in their migratory behavior. Our results show a functional cross-talk between CXCR4 and PDGFR which appears to be essential for GBM chemotaxis.

Exosome-based strategies for Diagnosis and Therapy

Exosomes are small extracellular vesicles (30-120 nm) of endosomal origin, which are gaining the attention of the scientific community. Originally considered only a waste disposal system, they are now emerging as another class of signal mediators. Exosomes are secreted by any cell type and retrieved in every body fluid, such as blood, urine, saliva and amniotic liquid. Remarkably, their biochemical content includes not only lipids and proteins, but also nucleic acids, mainly miRNA and mRNA, with a few reports also indicating the presence of genomic and mitochondrial DNA. Their properties have stimulated extensive research to exploit them as a source of biomarkers for the diagnosis and the follow-up of several pathologies. Furthermore, exosomes are relatively robust and stable, so they appear attractive as gene and drug delivery vehicles. They have also revealed immunomodulatory and regenerative properties, which are encouraging their application for therapeutic purposes. Several issues remain to be addressed: exosome isolation is still time consuming and unsatisfactorily reproducible, making it difficult to compare results among laboratories, improve our knowledge of their physiological function and correlate their features with pathological outcomes. Nevertheless, the number of patents trying to address these problems is growing exponentially and many novelties will reach the scientific community in the next few years.

A role for the autophagy regulator Transcription Factor EB in amiodarone-induced phospholipidosis.

The antiarrhythmic agent amiodarone, a cationic amphiphilic drug, is known to induce phospholipidosis, i.e. the accumulation of phospholipids within lysosomal structures to give multi-lamellar inclusion bodies. Despite the concerns raised about phospholipidosis in the recent years, the molecular mechanisms underlying amiodarone- or other cationic amphiphilic drug-induced phospholipidosis are still under investigation. Here we demonstrated that amiodarone doses able to induce phospholiposis according to NBD-PC uptake assay (1-12 μM, 24 h) activates Transcription Factor EB (TFEB), a pivotal regulator of the autophagic pathway, in human HepG2 cells. Further evidences confirmed the effect of amiodarone on the autophagic-lysosomal system in HepG2 and BEAS-2B cells: lysosomal β-hexosaminidase isoenzymes secretion, transcriptional up-regulation of the lysosomal β-hexosaminidase α-subunit, alteration of cathepsin B, D and L intracellular maturation in a cell- and protease-specific manner. Autophagy activation was also demonstrated by increased conversion of LC3-I into LC3-II and reduced phosphorylation of the mTORC1 target S6 kinase. Besides, we provided evidence that TFEB over-expression prevents amiodarone-induced phospholipid accumulation, suggesting that this transcription factor could be a possible target to develop strategies for phospholipidosis attenuation.

Phosphatidylserine metabolism modification precedes manganese- induced apoptosis and phosphatidylserine exposure in PC12 cells

Long-term exposure to high manganese (Mn) levels can lead to Parkinson-like neurological disorders. Molecular mechanisms underlying Mn cytotoxicity have been not defined. It is known that Mn induces apoptosis in PC12 cells and that this involves the activation of some signal transduction pathways. Although the role of phospholipids in apoptosis and signal transduction is well-known, the membrane phospholipid component in Mn-related damage has not yet been investigated. Phosphatidylserine (PS) facilitates protein translocation from cytosol to plasma membrane and PS exposure on the cell surface allows macrophage recognition of apoptotic cells. This study investigates the effects of MnCl2 on PS metabolism in PC12 cells, relating them to those on cell apoptosis. Apoptosis induction decreased PS radioactivity of PC12 cells incubated with radioactive serine. MnCl2 reduced PS radioactivity even under conditions that did not affect cell viability or PS exposure, suggesting that the effects on PS metabolism may represent an early event in cell apoptosis. Thus the latter conditions that also induced a greater PS decarboxylation were utilized for further investigating on the effects on PS synthesis, by measuring the activity and expression of PS-synthesizing enzymes, in cell lysates and in total cellular membranes (TM). Compared with corresponding controls, enzyme activity of MnCl2-treated cells was lower in cell lysates and greater in TM. Evaluating the expression of two isoforms of PS-synthesizing enzyme (PSS), PSSII was increased both in cell lysate and TM, while PSSI was unchanged. MnCl2 addition to control cell lysate reduced enzyme activity. These results suggest Mn plays a dual role on PS synthesis. Once inside the cell, Mn inhibits the enzyme/s, thus accounting for reduced PS synthesis in lysates and intact cells. On the other hand, it increases PSSII expression in cell membranes. The possibility that this occurs to counteract the direct effects of Mn ions on enzyme activity cannot be excluded. The effects on membrane enzyme activity and expression may also participate to PS exposure, observed at longer periods of treatment, by increasing membrane PS content.

Changes in Lipid Composition During Manganese-Induced Apoptosis in PC12 Cells

AbstractLipid composition of membranes is fundamental to modulate signaling pathways relying on lipid metabolites and/or membrane proteins, thus resulting in the regulation of important cell processes such as apoptosis. In this case, membrane remodeling is an early event important for the activation of signaling leading to cell death and removal of apoptotic cells. In the present study, we analyzed phospholipid, cholesterol and fatty acid content during apoptosis induced by manganese in PC12 cells. Lipid analysis of whole cells and detergent-resistant membranes was carried out by HPLC/GC. Results showed that apoptosis is associated with changes in lipid composition detectable in whole cell extracts, namely cholesterol, phosphatidylserine and phosphatidylethanolamine decreases. Noteworthy, phosphatidylserine level reduction was detectable before to the detection of apoptosis, in correlation with our previous study carried out by radioactive labelling. By contrast, phosphatidylserine and phosphatidylethanolamine changes were not detected in detergent resistant membranes, which instead showed an altered composition in phosphatidylinositol, phosphatidylcholine and sphingomyelin in apoptotic cells.

Presence of Phosphatidylserine Synthesizing Enzymes in Triton Insoluble Floating Fractions from Cerebrocortical Plasma Membranes

Mammals synthesize phosphatidylserine (PS), a binding PKC molecule, by exchanging the nitrogen base of phosphatidylethanolamine or phosphatidylcholine with free serine. Serine base exchange enzyme (SBEE) was found in Triton insoluble floating fractions (TIFFs) from rat cerebellum which contained PKC. Consequently, SBEE might modulate PS levels in the PKC binding area (Buratta et al., J Neurochem 103:942–951, 2007). In the present study, we determined whether SBEE and PKC were localised in rat cerebral cortex TIFFs (cx-TIFFs) and in rat cerebrocortical plasma membrane-TIFFs (PM-TIFFs) which are more directly involved in signal transduction than intracellular membranes. Cx-and PM-TIFFs expressed SBEE activity and contained PKC. SBEE used ethanolamine as free exchanging base which may modulate PS level in the PKC binding area, transforming PS into PE and vice versa. The slight decrease in [14C]serine incorporation in the presence of choline indicated the existence of a SBEE isoform which may play a peculiar role in this brain area.

Phosphatidylserine metabolism in human lymphoblastic cells exposed to chromium (VI).

Objective: Hexavalent chromium (Cr(VI)) compounds are widely found in different working environments. These compounds can cause apoptosis in human cells, but the mechanisms underlying chromium-induced apoptosis are not clear. A marker of apoptosis is the exposure of phosphatidylserine on cell membrane and the modification of phosphatidylserine metabolism. The aim of this study was to verify whether chromium could cause phosphatidylserine exposure and modification of its metabolism in human lymphoblastic leukemia cell line (MOLT-4). Methods: Phosphatidylserine exposure was evaluated by annexin V binding whereas phosphatidylserine metabolism was studied measuring the incorporation of [3H]serine. Results: Cell treatment with Cr(VI) increases phosphatidylserine exposure and cell apoptosis, but decreases the incorporation of [3H]serine into phosphatidylserine in a dose- and time-dependent manner. Conclusions: The Cr(VI)-induced apoptosis also through modification of phosphatidylserine exposure and metabolism.