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Glioblastoma (GBM) is one of the most aggressive cancers, characterized by a decrease in antioxidant levels. Evidence has demonstrated that ferulic acid (FA), a natural antioxidant particularly abundant in vegetables and fruits, could be a promising candidate for GBM treatment. Since FA shows a high instability that compromises its therapeutic application, it has been encapsulated into Nanostructured Lipid Carriers (NLCs) to improve its bioavailability in the brain. It has been demonstrated that tissue transglutaminase (TG2) is a multi-functional protein implicated in many physiological and pathological processes, including cancer. TG2 is also involved in GBM correlated with metastasis formation and drug resistance. Therefore, the evaluation of TG2 expression levels and its cellular localization are important to assess the anti-cancer effect of FA against GBM cancer. Our results have demonstrated that treatment with free FA and FA-NLCs in the U87-MG cancer cell line differently modified TG2 localization and expression levels. In the cells treated with free FA, TG2 appeared expressed both in the cytosol and in the nucleus, while the treatment with FA-NLCs showed that the protein is exclusively localized in the cytosol, exerting its pro-apoptotic effect. Therefore, our data suggest that FA loaded in NLCs could represent a promising natural agent for supplementing the current anti-cancer drugs used for the treatment of GBM.

Herein, we assessed the effect of full native peptide of amyloid-beta (Aβ) (1-42) and its fragments (25-35 and 35-25) on tissue transglutaminase (TG2) and its isoforms (TG2-Long and TG2-Short) expression levels on olfactory ensheathing cells (OECs). Vimentin and glial fibrillary acid protein (GFAP) were also studied. The effect of the pre-treatment with indicaxanthin from Opuntia ficus-indica fruit on TG2 expression levels and its isoforms, cell viability, total reactive oxygen species (ROS), superoxide anion (O 2 - ), and apoptotic pathway activation was assessed. The levels of Nestin and cyclin D1 were also evaluated. Our findings highlight that OECs exposure to Aβ(1-42) and its fragments induced an increase in TG2 expression levels and a different expression pattern of its isoforms. Indicaxanthin pre-treatment reduced TG2 overexpression, modulating the expression of TG2 isoforms. It reduced total ROS and O 2 - production, GFAP and Vimentin levels, inhibiting apoptotic pathway activation. It also induced an increase in the Nestin and cyclin D1 expression levels. Our data demonstrated that indicaxanthin pre-treatment stimulated OECs self-renewal through the reparative activity played by TG2. They also suggest that Aβ might modify TG2 conformation in OECs and that indicaxanthin pre-treatment might modulate TG2 conformation, stimulating neural regeneration in Alzheimer's disease.

Herein, we assessed in a particular glial cell type, called olfactory ensheathing cells (OECs), the effect of some growth factors (GFs) on tissue transglutaminase (TG2) overexpression induced by amyloid-beta (Aβ) with native full-length peptide 1-42 or by fragments, 25-35 or 35-25, as control. Previously, we demonstrated that TG2 overexpression induced by some stressors was down-regulated by GFs exposure in OECs. To monitor cell viability, an MTT test was used, while TG2 expression was examined using immunocytochemical and Western blot analysis. We also considered the involvement of the TG2-mediated apoptotic pathway. Vimentin expression was evaluated as well. Reactive oxygen species and reduced glutathione levels were utilized to test the oxidative intracellular status. Lactate dehydrogenase released into the medium, as a marker of necrotic cell death, was evaluated. We found that in OECs exposed to Aβ(1-42) or Aβ(25-35) for 24 h, TG2 expression increased, and we observed that the protein appeared prevalently localized in the cytosol. The pre-treatment with GFs, basic fibroblast growth factor (bFGF) or glial-derived neurotrophic factor (GDNF), down-regulated the TG2 level, which was prevalently limited to the nuclear compartment. Vimentin expression and caspase cleavage showed a significant enhancement in Aβ(1-42) and Aβ(25-35) exposed cells. The pre-treatment with bFGF or GDNF was able to restore the levels of the proteins to control values, and the intracellular oxidative status modified by the exposure to Aβ(1-42) or Aβ(25-35). Our data suggest that both bFGF or GDNF could be an innovative mechanism to contrast TG2 expression, which plays a key role in Alzheimer's disease.

Tissue transglutaminase (TG2), a multifunctional enzyme implicated in cellular proliferation and differentiation 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 lipopolysaccaride (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 particular 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., (Copyright © 2011 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.)