Carlo Maria Di Liegro

Oligodendroglioma cells shed microvesicles which contain TRAIL as well as molecular chaperones and induce cell death in astrocytes

Microvesicles (MVs) shed from G26/24 oligodendroglioma cells were previously reported to cause a reproducible, dose-dependent, inhibitory effect on neurite outgrowth, and eventually neuronal apoptosis, when added to primary cultures of rat cortical neurons. These effects were reduced but not abolished by functional monoclonal antibodies against Fas-L. In order to investigate whether MVs contain other factors able to induce cell death, we tested them for TRAIL and found clear evidence of its presence in the vesicles. This finding suggests the possibility that Fas-L and TRAIL cooperate in inducing brain cell death. Aimed at understanding the route through which the vesicles deliver their messages to the target cells, we labeled oligodendroglioma cells with radioactive methionine and then added the labeled vesicles shed from tumor cells to unlabeled astrocytes in culture. Here we report that labeled proteins were delivered to the test cells. In order to investigate whether astrocytes, like neurons, are sensitive to oligodendroglioma-derived vesicles, MVs were prepared from media conditioned by G26/24 oligodendroglioma cells and added to primary cultures of rat cortical astrocytes. These cells were clearly more resistant than neurons to microvesicle-induced damage: a high dose (40 µg) of shed MVs induced cell death in only about 40% of astrocytes. Finally, we demonstrated that Hsp70 is specifically enriched in MVs which also contain, even if at lower level, the Hsc70 constitutive chaperone.

Lactate as a Metabolite and a Regulator in the Central Nervous System

More than two hundred years after its discovery, lactate still remains an intriguing molecule. Considered for a long time as a waste product of metabolism and the culprit behind muscular fatigue, it was then recognized as an important fuel for many cells. In particular, in the nervous system, it has been proposed that lactate, released by astrocytes in response to neuronal activation, is taken up by neurons, oxidized to pyruvate and used for synthesizing acetyl-CoA to be used for the tricarboxylic acid cycle. More recently, in addition to this metabolic role, the discovery of a specific receptor prompted a reconsideration of its role, and lactate is now seen as a sort of hormone, even involved in processes as complex as memory formation and neuroprotection. As a matter of fact, exercise offers many benefits for our organisms, and seems to delay brain aging and neurodegeneration. Now, exercise induces the production and release of lactate into the blood which can reach the liver, the heart, and also the brain. Can lactate be a beneficial molecule produced during exercise, and offer neuroprotection? In this review, we summarize what we have known on lactate, discussing the roles that have been attributed to this molecule over time.

Regulation of mRNA transport, localization and translation in the nervous system of mammals (Review)

Post-transcriptional control of mRNA trafficking and metabolism plays a critical role in the actualization and fine tuning of the genetic program of cells, both in development and in differentiated tissues. Cis-acting signals, responsible for post-transcriptional regulation, reside in the RNA message itself, usually in untranslated regions, 5′ or 3′ to the coding sequence, and are recognized by trans-acting factors: RNA-binding proteins (RBPs) and/or non-coding RNAs (ncRNAs). ncRNAs bind short mRNA sequences usually present in the 3′-untranslated (3′-UTR) region of their target messages. RBPs recognize specific nucleotide sequences and/or secondary/tertiary structures. Most RBPs assemble on mRNA at the moment of transcription and shepherd it to its destination, somehow determining its final fate. Regulation of mRNA localization and metabolism has a particularly important role in the nervous system where local translation of pre-localized mRNAs has been implicated in developing axon and dendrite pathfinding, and in synapse formation. Moreover, activity-dependent mRNA trafficking and local translation may underlie long-lasting changes in synaptic efficacy, responsible for learning and memory. This review focuses on the role of RBPs in neuronal development and plasticity, as well as possible connections between ncRNAs and RBPs.

Extracellular Membrane Vesicles as Vehicles for Brain Cell-to-Cell Interactions in Physiological as well as Pathological Conditions

Extracellular vesicles are involved in a great variety of physiological events occurring in the nervous system, such as cross talk among neurons and glial cells in synapse development and function, integrated neuronal plasticity, neuronal-glial metabolic exchanges, and synthesis and dynamic renewal of myelin. Many of these EV-mediated processes depend on the exchange of proteins, mRNAs, and noncoding RNAs, including miRNAs, which occurs among glial and neuronal cells. In addition, production and exchange of EVs can be modified under pathological conditions, such as brain cancer and neurodegeneration. Like other cancer cells, brain tumours can use EVs to secrete factors, which allow escaping from immune surveillance, and to transfer molecules into the surrounding cells, thus transforming their phenotype. Moreover, EVs can function as a way to discard material dangerous to cancer cells, such as differentiation-inducing proteins, and even drugs. Intriguingly, EVs seem to be also involved in spreading through the brain of aggregated proteins, such as prions and aggregated tau protein. Finally, EVs can carry useful biomarkers for the early diagnosis of diseases. Herein we summarize possible roles of EVs in brain physiological functions and discuss their involvement in the horizontal spreading, from cell to cell, of both cancer and neurodegenerative pathologies.

Confocal microscopy study of the distribution, content and activity of mitochondria during Paracentrotus lividus development

In the present paper we applied confocal microscopy and fluorescence technologies for studying the distribution and the oxidative activity of sea urchin (Paracentrotus lividus) mitochondria during development, by in vivo incubating eggs and embryos with cell‐permeant MitoTracker probes. We calculated, by a mathematical model, the intensity values, the variations of intensity, and the variation index of incorporated fluorochromes. Data demonstrate that mitochondrial mass does not change during development, whereas mitochondrial respiration increases. In addition, starting from 16 blastomeres stage, some regions of the embryo contain organelles more active in oxygen consumption.

Aquaporins and Brain Tumors

Brain primary tumors are among the most diverse and complex human cancers, and they are normally classified on the basis of the cell-type and/or the grade of malignancy (the most malignant being glioblastoma multiforme (GBM), grade IV). Glioma cells are able to migrate throughout the brain and to stimulate angiogenesis, by inducing brain capillary endothelial cell proliferation. This in turn causes loss of tight junctions and fragility of the blood–brain barrier, which becomes leaky. As a consequence, the most serious clinical complication of glioblastoma is the vasogenic brain edema. Both glioma cell migration and edema have been correlated with modification of the expression/localization of different isoforms of aquaporins (AQPs), a family of water channels, some of which are also involved in the transport of other small molecules, such as glycerol and urea. In this review, we discuss relationships among expression/localization of AQPs and brain tumors/edema, also focusing on the possible role of these molecules as both diagnostic biomarkers of cancer progression, and therapeutic targets. Finally, we will discuss the possibility that AQPs, together with other cancer promoting factors, can be exchanged among brain cells via extracellular vesicles (EVs).

Oligodendroglioma cells synthesize the differentiation-specific linker histone H1˚ and release it into the extracellular environment through shed vesicles

Chromatin remodelling can be involved in some of the epigenetic modifications found in tumor cells. One of the mechanisms at the basis of chromatin dynamics is likely to be synthesis and incorporation of replacement histone variants, such as the H1° linker histone. Regulation of the expression of this protein can thus be critical in tumorigenesis. In developing brain, H1° expression is mainly regulated at the post-transcriptional level and RNA-binding proteins (RBPs) are involved. In the past, attention mainly focused on the whole brain or isolated neurons and little information is available on H1° expression in other brain cells. Even less is known relating to tumor glial cells. In this study we report that, like in maturing brain and isolated neurons, H1° synthesis sharply increases in differentiating astrocytes growing in a serum-free medium, while the corresponding mRNA decreases. Unexpectedly, in tumor glial cells both H1° RNA and protein are highly expressed, in spite of the fact that H1° is considered a differentiation-specific histone variant. Persistence of H1° mRNA in oligodendroglioma cells is accompanied by high levels of H1° RNA-binding activities which seem to be present, at least in part, also in actively proliferating, but not in differentiating, astrocytes. Finally, we report that oligodendroglioma cells, but not astrocytes, release H1° protein into the culture medium by shedding extracellular vesicles. These findings suggest that deregulation of H1° histone expression can be linked to tumorigenesis.

Qualitative differences in nuclear proteins correlate with neuronal terminal differentiation

Summary1.Protein composition of neuronal nuclei was studied at two stages of brain maturation, i.e., before (embryonic day 16; E16) and after (postnatal day 10; P10) shortening of the nucleosomal repeat length. Glial nuclei were analyzed in parallel as a control.2.Total nuclear or HCl- and 5% perchloric acid (PCA)-soluble proteins were analyzed by different electrophoretic techniques.3.Our results show an increase in the concentration of histone H1° with differentiation, although the H1 class undergoes an overall decrease.4.The chromatin of mature neurons is also enriched in the ubiquinated form of histone H2A (A24), while the high-mobility group (HMG) proteins 1 and 2 seem to decrease slightly relative to core histones.5.Both quantitative and qualitative differences in the abundance of nonhistone proteins relative to histones accompany neuronal terminal differentiation.

The dynamic properties of neuronal chromatin are modulated by triiodothyronine

The effect of triiodothyronine (T3) on the rate of synthesis of nuclear proteins was studied during terminal differentiation of rat cortical neurons cultured in a serum-free medium. To this aim total and acid soluble nuclear proteins were analyzed by different electrophoretic techniques. Our results show that: 1) during maturation in vitro, neuronal nuclei undergo a dramatic change in the rate at which different classes of histones and high mobility group (HMG) proteins are synthesized; the synthetic activity, measured as incorporation of radioactive precursors into nuclear proteins, slows indeed down with age: especially evident is the decrease in core histones synthesis; at day 15, on the other hand, HMG 14 and 17 and ubiquitinated H2A (A24) are synthesized at a high rate, especially in T3-treated neurons; 2) neurons treated with T3 show, at any age tested, a higher level of lysine incorporation into nuclear proteins; 3) even if during the first days of culture neurons synthesize core histones more actively in the presence of T3, there is no accumulation of these proteins at later stages, as compared with untreated cells. Possible implications of these data and relationship with the chromatin rearrangement which accompanies neuronal terminal differentiation are discussed.

Accumulation of different c-erbA transcripts during rat brain development and in cortical neurons cultured in a synthetic medium

Summary1.Accumulation of different c-erbA transcripts was studied, during rat brain maturation and in cortical neurons differentiating in a serum-free medium, by quantitative Northern blot hybridization.2.Theα andβ forms of c-erbA mRNAs exhibit different patterns of accumulation, with a precocious increase in theα forms compared with theβ forms bothin vivo and in culture.3.erbAα2 mRNA (2.6 kb) is by far the predominant form, with a maximum at birth (PO).4.The accumulation patterns of bothα andβ forms show discrete differences in isolated neurons compared to brain cortices; in particular the pattern ofα2 mRNA accumulation in culture suggests its predominant localization to neurons.5.The presence of T3 in the culture medium does not have significant effects on the level of any of erbA mRNAs.6.Possible implications and relationships with neuronal terminal differentiation are discussed.