Neuroscience Research 72 (2012) 289–295 Contents lists available at SciVerse ScienceDirect Neuroscience Research jo u r n al hom ep age: www.elsevier.com/locate/neures Expression of tissue transglutaminase on primary olfactory ensheathing cells cultures exposed to stress conditions Agata Campisi a , Michela Spatuzza c , Antonella Russo b , Giuseppina Raciti a , Angelo Vanella a , Stefania Stanzani b , Rosalia Pellitteri c,∗ a Department of Drug Sciences, University of Catania, Viale A. Doria 6, 95125 Catania, Italy b Department of Physiological Sciences, University of Catania, Viale A. Doria 6, 95125 Catania, Italy c Institute of Neurological Sciences, National Research Council, Section of Catania, via P. Gaifami 18, 95126 Catania, Italy a r t i c l e i n f o Article history: Received 28 September 2011 Received in revised form 14 December 2011 Accepted 15 December 2011 Available online 24 December 2011 Keywords: Olfactory ensheathing cells Tissue transglutaminase Growth Factors Stress conditions Immunocytochemistry Glial cultures a b s t r a c t Tissue transglutaminase (TG2), a multifunctional enzyme implicated in cellular proliferation and differ- entiation processes, plays a modulatory role in the cell response to stressors. Herein, we used olfactory ensheathing cells (OECs), representing an unusual population of glial cells to promote axonal regeneration and to provide trophic support, as well as to assess whether the effect of some Growth Factors (GFs), NGF, bFGF or GDNF, on TG2 overexpression induced by stress conditions, such as glutamate or lipopolysac- caride (LPS). Glial Fibrillary Acidic Protein (GFAP) and vimentin were used as markers of astroglial differentiation and cytoskeleton component, respectively. Glutamate or LPS treatment induced a particu- lar increase of TG2 expression. A pre-treatment of the cells with the GFs restored the levels of the protein to that of untreated ones. Our results demonstrate that the treatment of OECs with the GFs was able to restore the OECs oxidative status as modified by stress, also counteracting TG2 overexpression. It suggests that, in OECs, TG2 modulation or inhibition induced by GFs might represent a therapeutic target to control the excitotoxicity and/or inflammation, which are involved in several acute and chronic brain diseases. © 2011 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved. 1. Introduction Tissue transglutaminase (TG2) is a member of the transglu- taminases (TGases) families of thioldependent enzymes catalyzing calcium-dependent peptide cross-linking, polyamination, or deam- ination reactions at glutamine residues within specific protein substrates (Lorand and Graham, 2003). It has been reported that a dysregulation of TG2 may contribute to the pathogenesis of many acute and chronic brain diseases (Lesort et al., 2000). TG2 has been found in the cytosol, in mitochondria (Piacentini et al., 2002) and in the nucleus (Campisi et al., 2003). It pos- sesses disulfide isomerase (Hasegawa et al., 2003), kinase as well as protein scaffold functions and GTPase activity (Nakaoka et al., 1994). The multiple functions of TG2 also depend on its intra- cellular location. In fact, when TG2 was localized in the cytosol differentially modulates apoptosis in a stimuli-dependent man- ner, and its transamidating activity is essential for its pro-apoptotic Abbreviations: TG2, tissue transglutaminase; OECs, olfactory ensheathing cells; GFs, Growth Factors; MTT, 3(4,5-dimethyl-thiazol-2-yl)2,5-diphenyl-tetrazolium bromide; LDH, lactate dehydrogenase; LPS, lipopolysaccaride; GSH, glutathione; ROS, reactive oxygen species. ∗ Corresponding author. Tel.: +39 095 7338131; fax: +39 095 7338110. E-mail address: r.pellitteri@isn.cnr.it (R. Pellitteri). effects (Milakovic et al., 2004). In contrast, when TG2 is localized into the nuclear compartment, it phosphorylates several proteins, including retinoblastoma protein (Rb), a substrate for TG2 kinase activity (Mishra et al., 2007). Furthermore, TG2 is responsible for the phosphorylation of Insulin-like Growth Factor (IGF)-binding protein-3 (IGFBP-3; Mishra and Murphy, 2004) that also exerts IGF- independent pro-apoptotic effects in various cell types (Valentinis and Baserga, 1996). Our recent studies have shown an interaction between Growth Factors (GFs) and steroids on TG2 expression in primary rat astroglial cell cultures (Campisi et al., 2008). An unusual population of glial cells are olfactory ensheath- ing cells (OECs) that ensheathe unmyelinated olfactory axons, and share many phenotypic properties with astrocytes and Schwann cells (SCs; Mackay-Sim, 2005; Ramon-Cueto and Avila, 1998). Immunocytochemical studies have revealed that OECs are a source of GFs, including NGF, BDNF, GDNF, NT-3 (Woodhall et al., 2001), CNTF (Wewetzer et al., 2001), and express different markers, such as GFAP, p75, NGFr, vimentin, laminin, S-100 protein, and N- CAM (Pellitteri et al., 2010). The regenerative properties of these cells have inspired neuroscientists to explore their ability to sup- port axonal regeneration when transplanted, as OECs are able to remyelinate axons, and improve functional recovery after spinal cord injury (Raisman, 2007; Su and He, 2010). In previous studies, it has been demonstrated that TG2 was up-regulated in primary 0168-0102/$ – see front matter © 2011 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved. doi:10.1016/j.neures.2011.12.008