Genomic and Non-genomic Action of Neurosteroids in the Peripheral Nervous System

Since the former evidence of biologic actions of neurosteroids in the central nervous system, also the peripheral nervous system (PNS) was reported as a structure affected by these substances. Indeed, neurosteroids are synthesized and active in the PNS, exerting many important actions on the different cell types of this system. PNS is a target for neurosteroids, in their native form or as metabolites. In particular, old and recent evidence indicates that the progesterone metabolite allopregnanolone possesses important functions in the PNS, thus contributing to its physiologic processes. In this review, we will survey the more recent findings on the genomic and non-genomic actions of neurosteroids in nerves, ganglia, and cells forming the PNS, focusing on the mechanisms regulating the peripheral neuron-glial crosstalk. Then, we will refer to the physiopathological significance of the neurosteroid signaling disturbances in the PNS, in to identify new molecular targets for promising pharmacotherapeutic approaches

Neurosteroids involvement in the epigenetic control of memory formation and storage

Memory is our ability to store and remember past experiences; it is the result of changes in neuronal circuits of specific brain areas as the hippocampus. During memory formation, neurons integrate their functions and increase the strength of their connections, so that synaptic plasticity is improved and consolidated. All these processes recruit several proteins at the synapses, whose expression is highly regulated by DNA methylation and histone tails posttranslational modifications. Steroids are known to influence memory process, and, among them, neurosteroids are implicated in neurodegenerative disease related to memory loss and cognitive impairment. The epigenetic control of neurosteroids involvement in memory formation and maintenance could represent the basis for neuroregenerative therapies

M2 muscarinic receptor activation inhibits cell proliferation and migration of rat adipose-mesenchymal stem cells

Mesenchymal stem cells (MSCs), also known as stromal mesenchymal stem cells, are multipotent cells, which can be found in many tissues and organs as bone marrow, adipose tissue and other tissues. In particular MSCs derived from Adipose tissue (ADSCs) are the most frequently used in regenerative medicine because they are easy to source, rapidly expandable in culture and excellent differentiation potential into adipocytes, chondrocytes and other cell types. Acetylcholine (ACh), is one of the most important neurotransmitter in central (CNS) and peripheral nervous system (PNS), playing important roles also in non-neural tissue, but its functions in MSCs are still not investigated. Although MSCs express muscarinic receptor subtypes, their role is completely unknown. In present work muscarinic cholinergic effects were characterized in rat ADSCs. Analysis by RT-PCR demonstrates that ADSCs express M1-M4 muscarinic receptor subtypes, whereas M2 is one of the most expressed subtype. For this reason, our attention was focused on M2 subtype. By using the selective M2 agonist Arecaidine Propargyl Ester (APE) we performed cell proliferation and migration assays demonstrating that APE causes cell growth and migration inhibition without affecting cell survival. Our results indicate that ACh via M2 receptors, may contribute to the maintaining of the ADSCs quiescent status. These data are the first evidence that ACh via muscarinic receptors might contribute to control ADSCs physiology

Regulation of Schwann cells oncotransformation by changes in Nf2/merlin expression, Hippo/YAP signaling and DNA methylation

Schwann cell (SC) express the Neurofibromin type 2 gene (Nf2), encoding the tumor suppressor protein merlin, a cytoskeleton-associated protein regulating cell proliferation and survival. Nf2/merlin inactivation causes protein loss and leads to SC transformation into a form of benign tumor called schwannoma. Moreover, Nf2/merlin is mutated in an autosomal dominant multiple syndrome, called neurofibromatosis type 2. In line with observation that physio/mechanical cues, such as environmental challenges, may be pathogenetically relevant for SC oncotransformation, we recently showed that the exposure to electromagnetic fields (EMFs) causes changes in SC Nf2/merlin expression, cell migration, chemotactic responsivity and cytoskeleton reorganization. We showed a downstream MAPK/Erk activation, involved in SC proliferation, as well as activation of Hippo/YAP signalling commonly altered during tumorigenesis. We also showed that some genes, known to be upstream or downstream mediators of Hippo (Amotl2, Dchs, Fat, Wnt1) were changed. Further studies on rat SC oncotransformation following acute EMF exposure (0.1 T, 50 Hz, 10 min) demonstrated that the number of cells in G1 phase was increased. Focus forming analysis, after repeated exposures, showed an increase in 3D SC growth. EMF affects also the SC epigenome, as total DNA methylation, de novo DNMT and HDAC were reduced. Furthermore, RT2-profile assay evidenced that genes crucial for SCs are upregulated in EMF exposed cells. Overall, we identified some mechanisms responsible of environmental-induced SC changes toward a proliferative/migrating state, which may be pathologically relevant for nerve tumor development

Current trends in polymer based sensors

This review illustrates various types of polymer and nanocomposite polymeric based sensors used in a wide variety of devices. Moreover, it provides an overview of the trends and challenges in sensor research. As fundamental components of new devices, polymers play an important role in sensing applications. Indeed, polymers offer many advantages for sensor technologies: their manufacturing methods are pretty simple, they are relatively low-cost materials, and they can be functionalized and placed on different substrates. Polymers can participate in sensing mechanisms or act as supports for the sensing units. Another good quality of polymer-based materials is that their chemical structure can be modified to enhance their reactivity, biocompatibility, resistance to degradation, and flexibility

Steroid metabolism and effects in central and peripheral glial cells

Hormonal steroids participate in the control of a large number of functions of the central nervous system (CNS); recent data show that they may also intervene at the level of the peripheral nervous system (PNS). Both the CNS and the PNS metabolize endogenous as well as exogenous steroids; one of the major enzymatic system is represented by the 5alpha-reductase-3alpha-hydroxysteroid complex. This is a versatile system, since every steroid possessing the delta 4-3keto configuration (e.g., testosterone, progesterone, deoxycorticosterone) may be a substrate. High levels of 5alpha-reductase are found in the white matter of the CNS and in purified myelin. The observation that, in addition to neurons, glia may be a target for steroid action is an important recent finding. The effects of progesterone, testosterone, corticoids, and their respective 5alpha and 3alpha-5alpha derivatives on the expression of glial genes are presented and discussed. It has also been found that progesterone and/or its 5alpha-reduced metabolites increase the mRNA for the two major proteins of peripheral myelin, the glycoprotein Po and the peripheral myelin protein 22, in the sciatic nerve of normal and aged animals and in Schwann cells. The hypothesis has been put forward that glycoprotein Po might be under the control of progestagens acting mainly via the progesterone receptor, and that peripheral myelin protein 22 might be controlled via an interaction of steroids with the gamma-aminobutyric acid (GABA)ergic system. It is known that tetrahydroprogesterone, the 3alpha-5alpha-reduced metabolite of progesterone, interacts with the GABA(A) receptor. Our recent data show that several subunits of this receptor are present in sciatic nerve as well as in Schwann cells that reside in this nerve. These data open multiple possibilities for new therapeutic approaches to demyelinating diseases

Schwann Cell Autocrine and Paracrine Regulatory Mechanisms, Mediated by Allopregnanolone and BDNF, Modulate PKCε in Peripheral Sensory Neurons

Protein kinase type C-\u3b5 (PKC\u3b5) plays important roles in the sensitization of primary afferent nociceptors, such as ion channel phosphorylation, that in turn promotes mechanical hyperalgesia and pain chronification. In these neurons, PKC\u3b5 is modulated through the local release of mediators by the surrounding Schwann cells (SCs). The progesterone metabolite allopregnanolone (ALLO) is endogenously synthesized by SCs, whereas it has proven to be a crucial mediator of neuron-glia interaction in peripheral nerve fibers. Biomolecular and pharmacological studies on rat primary SCs and dorsal root ganglia (DRG) neuronal cultures were aimed at investigating the hypothesis that ALLO modulates neuronal PKC\u3b5, playing a role in peripheral nociception. We found that SCs tonically release ALLO, which, in turn, autocrinally upregulated the synthesis of the growth factor brain-derived neurotrophic factor (BDNF). Subsequently, glial BDNF paracrinally activates PKC\u3b5 via trkB in DRG sensory neurons. Herein, we report a novel mechanism of SCs-neuron cross-talk in the peripheral nervous system, highlighting a key role of ALLO and BDNF in nociceptor sensitization. These findings emphasize promising targets for inhibiting the development and chronification of neuropathic pain

Tumor suppressor Nf2/merlin drives Schwann cell changes following electromagnetic field exposure through Hippo-dependent mechanisms

Previous evidence showed mutations of the neurofibromin type 2 gene (Nf2), encoding the tumor suppressor protein merlin, in sporadic and vestibular schwannomas affecting Schwann cells (SC). Accordingly, efforts have been addressed to identify possible factors, even environmental, that may regulate neurofibromas growth. In this context, we investigated the exposure of SC to an electromagnetic field (EMF), which is an environmental issue modulating biological processes. Here we show that SC exposed to 50 Hz EMFs change their morphology, proliferation, migration and myelinating capability. In these cells merlin is downregulated, leading to activation of two intracellular signaling pathways, ERK/AKT and Hippo. Interestingly, SC change their phenotype toward a proliferative/migrating state, which in principle may be pathologically relevant for schwannoma development

Biodegradable hydrogels as scaffolds for nerve regeneration

Biodegradable hydrogels as scaffolds for nerve regeneration Valerio Magnaghi 1, Elisabetta Ranucci 2, Fabio Fenili 2, Patrizia Procacci 3, Giorgio Pivato 4, Paolo Cortese 4 and Paolo Ferruti 2 1 Department of Endocrinology, Physiopathology, Applied biology, Via Balzaretti 9, University of Milan, 20133 Milan, Italy 2 Department of Organic and Industrial Chemistry, University of Milan, Via Venezian 21, 20133 Milan, Italy 3 Department of Human Morphology and Biomedical Sciences - Citta' Studi, University of Milan, Via Mangiagalli 31, 20133 Milan, Italy 4 Hand Surgery Unit, IRCCS Multimedica, Via Milanese 300, 20099 Sesto San Giovanni, Italy Transected peripheral nerves are typically reconnected by direct end-to-end surgery or by autologous nerve graft. However, artificial synthetic guide are a successful alternative which may prevent neuroma formation (1). Among biodegradable conduits a novel approach is represented by use of tuneable polyamidoamine (PAA)-based hydrogels, with specific diameters, different shapes and/or dimensions. Depending by their crosslinking degree, hydrogels made by PAAs are tough material which may absorb large amounts of water. PAA hydrogels are biocompatible and biodegradable in vitro to non-toxic low molecular weight products over a period of time varying from few weeks to months (2). In order to evaluate their ability to promote nerve regeneration, PAA hydrogels scaled as scaffold conduits (10mm lenght, 1mm internal diameter) were studied by using an experimental model of rat nerve transection. A conduit was used to join a gap of 4-5 mm in the sciatic nerve, and a longitudinal analysis was made at 30, 45, 60, 90 days post-surgery. We performed the gait analysis to evaluate locomotor coordination, the plantar test to study nociception and pain sensitivity, and the morphological-morphometric analysis to evaluate the nerve recovery. Preliminary results indicate that nerve ends can be successfully joined by these PAA-based hydrogel conduits. One month after surgery, in fact, the regeneration is appreciable inside the conduit and the nerve is resistant to mechanical traction, without signs of inflammation or serum infiltrate. In the implanted rats 45 days after surgery the footprints analysis reveals a trail similar to sham-operated animals, while the thermal hypersensitivity tend to normalize to the control levels at later times. The morphological evaluation of the explanted conduit at 90 days after surgery shows normal myelin structures, confirming nerve regeneration and complete scaffold re-absorption. In conclusion, our results demonstrate that PAA hydrogels might be a promising scaffold tube for nerve regeneration. Further studies on the hydrogels functionalization for drug delivery, with growth factors or hormones, are in progress in our labs. References 1. Yannas, I.V., Hill, B.J., 2004. Selection of biomaterials for peripheral nerve regeneration using data from the nerve chamber model. Biomaterials 25, 1593-1600. 2. Jacchetti, E., Elimitri, E., Rodighiero, S., Indrieri, M., Gianfelice, A., Lenardi, C., Podest\ue0, A., Ranucci, E., Ferruti, P. Milani, P., 2008. P. Biomimetic poly(amidoamine) hydrogels as synthetic materials for cell culture. J. Biothecnol. 6, 1