Effect of Some Growth Factors on Tissue Transglutaminase Overexpression Induced by β-Amyloid in Olfactory Ensheathing Cells

Potential therapeutic effect of olfactory ensheathing cells in neurological diseases: neurodegenerative diseases and peripheral nerve injuries

Neurological diseases are destructive, mainly characterized by the failure of endogenous repair, the inability to recover tissue damage, resulting in the increasing loss of cognitive and physical function. Although some clinical drugs can alleviate the progression of these diseases, but they lack therapeutic effect in repairing tissue injury and rebuilding neurological function. More and more studies have shown that cell therapy has made good achievements in the application of nerve injury. Olfactory ensheathing cells (OECs) are a special type of glial cells, which have been proved to play an important role as an alternative therapy for neurological diseases, opening up a new way for the treatment of neurological problems. The functional mechanisms of OECs in the treatment of neurological diseases include neuroprotection, immune regulation, axon regeneration, improvement of nerve injury microenvironment and myelin regeneration, which also include secreted bioactive factors. Therefore, it is of great significance to better understand the mechanism of OECs promoting functional improvement, and to recognize the implementation of these treatments and the effective simulation of nerve injury disorders. In this review, we discuss the function of OECs and their application value in the treatment of neurological diseases, and position OECs as a potential candidate strategy for the treatment of nervous system diseases.

Effect of Astaxanthin on Tissue Transglutaminase and Cytoskeletal Protein Expression in Amyloid-Beta Stressed Olfactory Ensheathing Cells: Molecular and Delayed Luminescence Studies

Astaxanthin, a natural compound of Haematococcus pluvialis, possesses antioxidant, anti-inflammatory, anti-tumor and immunomodulatory activities. It also represents a potential therapeutic in Alzheimer’s disease (AD), that is related to oxidative stress and agglomeration of proteins such as amyloid-beta (Aβ). Aβ is a neurotoxic protein and a substrate of tissue transglutaminase (TG2), an ubiquitary protein involved in AD. Herein, the effect of astaxanthin pretreatment on olfactory ensheathing cells (OECs) exposed to Aβ(1–42) or by Aβ(25–35) or Aβ(35–25), and on TG2 expression were assessed. Vimentin, GFAP, nestin, cyclin D1 and caspase-3 were evaluated. ROS levels and the percentage of cell viability were also detected. In parallel, delayed luminescence (DL) was used to monitor mitochondrial status. ASTA reduced TG2, GFAP and vimentin overexpression, inhibiting cyclin D1 levels and apoptotic pathway activation which induced an increase in the nestin levels. In addition, significant changes in DL intensities were particularly observed in OECs exposed to Aβ toxic fragment (25–35), that completely disappear when OECs were pre-incubated in astaxantin. Therefore, we suggest that ASTA pre-treatment might represent an innovative mechanism to contrast TG2 overexpression in AD.

Redox Properties, Bioactivity and Health Effects of Indicaxanthin, a Bioavailable Phytochemical from Opuntia ficus indica, L.: A Critical Review of Accumulated Evidence and Perspectives

Phytochemicals from plant foods are considered essential to human health. Known for their role in the adaptation of plants to their environment, these compounds can induce adaptive responses in cells, many of which are directed at maintaining the redox tone. Indicaxanthin is a long-known betalain pigment found in the genus Opuntia of cactus pear and highly concentrated in the edible fruits of O. ficus indica, L. whose bioactivity has been overlooked until recently. This review summarizes studies conducted so far in vitro and in vivo, most of which have been performed in our laboratory. The chemical and physicochemical characteristics of Indicaxanthin are reflected in the molecule's reducing properties and antioxidant effects and help explain its ability to interact with membranes, modulate redox-regulated cellular pathways, and possibly bind to protein molecules. Measurement of bioavailability in volunteers has been key to exploring its bioactivity; amounts consistent with dietary intake, or plasma concentration after dietary consumption of cactus pear fruit, have been used in experimental setups mimicking physiological or pathophysiological conditions, in cells and in animals, finally suggesting pharmacological potential and relevance of Indicaxanthin as a nutraceutical. In reporting experimental results, this review also aimed to raise questions and seek insights for further basic research and health promotion applications.

Effect of Unloaded and Curcumin-Loaded Solid Lipid Nanoparticles on Tissue Transglutaminase Isoforms Expression Levels in an Experimental Model of Alzheimer’s Disease

Alzheimer’s disease (AD) is a neurodegenerative disease representing the most prevalent cause of dementia. It is also related to the aberrant amyloid-beta (Aβ) protein deposition in the brain. Since oxidative stress is involved in AD, there is a possible role of antioxidants present in the effected person’s diet. Thus, we assessed the effect of the systemic administration of solid lipid nanoparticles (SLNs) to facilitate curcumin (CUR) delivery on TG2 isoform expression levels in Wild Type (WT) and in TgCRND8 (Tg) mice. An experimental model of AD, which expresses two mutated human amyloid precursor protein (APP) genes, was used. Behavioral studies were also performed to evaluate the improvement of cognitive performance and memory function induced by all treatments. The expression levels of Bcl-2, Cyclin-D₁, and caspase-3 cleavage were evaluated as well. In this research, for the first time, we demonstrated that the systemic administration of SLNs-CUR, both in WT and in Tg mice, allows one to differently modulate TG2 isoforms, which act either on apoptotic pathway activation or on the ability of the protein to repair cellular damage in the brains of Tg mice. In this study, we also suggest that SLNs-CUR could be an innovative tool for the treatment of AD.

Amyloid-Beta Induces Different Expression Pattern of Tissue Transglutaminase and Its Isoforms on Olfactory Ensheathing Cells: Modulatory Effect of Indicaxanthin

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 (O₂⁻), 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 O₂⁻ 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.

Astaxanthin-Loaded Stealth Lipid Nanoparticles (AST-SSLN) as Potential Carriers for the Treatment of Alzheimer's Disease: Formulation Development and Optimization

Alzheimer's disease (AD) is a neurodegenerative disorder associated with marked oxidative stress at the level of the brain. Recent studies indicate that increasing the antioxidant capacity could represent a very promising therapeutic strategy for AD treatment. Astaxanthin (AST), a powerful natural antioxidant, could be a good candidate for AD treatment, although its use in clinical practice is compromised by its high instability. In order to overcome this limit, our attention focused on the development of innovative AST-loaded stealth lipid nanoparticles (AST-SSLNs) able to improve AST bioavailability in the brain. AST-SSLNs prepared by solvent-diffusion technique showed technological parameters suitable for parenteral administration (<200 nm). Formulated nanosystems were characterized by calorimetric studies, while their toxicological profile was evaluated by the MTT assay on the stem cell line OECs (Olfactory Ensheathing Cells). Furthemore, the protective effect of the nanocarriers was assessed by a long-term stability study and a UV stability assay confirming that the lipid shell of the nanocarriers was able to preserve AST concentration in the formulation. SSLNs were also capable of preserving AST's antioxidant capacity as demonstrated in the oxygen radical absorbance capacity (ORAC) assay. In conclusion, these preliminary studies outline that SSLNs could be regarded as promising carriers for systemic administration of compounds such as AST aimed at AD treatment.

Dynamic changes in cytoskeleton proteins of olfactory ensheathing cells induced by radiofrequency electromagnetic fields

Several evidences have suggested the ability of radiofrequency electromagnetic fields to influence biological systems, even if the action mechanisms are not well understood. There are few data on the effect of radiofrequency electromagnetic fields on self-renewal of neural progenitor cells. A particular glial type that shows characteristics of stem cells is olfactory ensheathing cells (OECs). Herein, we assessed the non-thermal effects induced on OECs through radiofrequency electromagnetic fields changing the envelope of the electromagnetic wave. Primary OEC cultures were exposed to continuous or amplitude-modulated 900 MHz electromagnetic fields, in the far-field condition and at different exposure times (10, 15, 20 min). The expression of OEC markers (S-100 and nestin), cytoskeletal proteins (GFAP and vimentin), apoptotic pathway activation by caspase-3 cleavage and cell viability were evaluated. Our results highlight that 20 min of exposure to continuous or amplitude-modulated 900 MHz electromagnetic fields induced a different and significant decrease in cell viability. In addition, according to the electromagnetic field waveform, diverse dynamic changes in the expression of the analysed markers in OECs and activation of the apoptotic pathway were observed. The data suggest that radiofrequency electromagnetic fields might play different and important roles in the self-renewal of OEC stem cells, which are involved in nervous system repair.

1,2,4-Oxadiazole-5-ones as analogues of tamoxifen: synthesis and biological evaluation

A series of 2,3,4-triaryl-substituted 1,2,4-oxadiazole-5-ones have been prepared as fixed-ring analogues of tamoxifen (TAM), a drug inhibitor of Estradiol Receptor (ER) used in breast cancer therapy, by an efficient synthetic protocol based on a 1,3-dipolar cycloaddition of nitrones to isocyanates. Some of the newly synthesized compounds (14d-f, 14h and 14k) show a significant cytotoxic effect in a human breast cancer cell line (MCF-7) possessing IC50 values between 15.63 and 31.82 μM. In addition, compounds 14d-f, 14h and 14k are able to increase the p53 expression levels, activating also the apoptotic pathway. Molecular modeling studies of novel compounds performed on the crystal structure of ER reveal the presence of strong hydrophobic interactions with the aromatic rings of the ligands similar to TAM. These data suggest that 1,2,4-oxadiazole-5-ones can be considered analogues of TAM, and that their anticancer activity might be partially due to ER inhibition.

Non thermal effects of radiofrequency electromagnetic field exposure on neural cells

The non-thermal mechanisms, underlying the damage induced on human cells by radiofrequency electromagnetic fields (RF-EMFs), are still unclear and only few studies reported about the effect of RFEMFs on self-renewal of neural progenitor cells. In this research, we investigated the influence of low-intensity RF-EMFs on Olfactory Ensheathing Cell (OEC) cultures, typical glia cells showing characteristics of stem cells. Cell cultures were exposed, in far-field condition, at 900 MHz continuous and amplitude modulated EMFs for 10, 15 and 20 min at 37°C. The expression of OEC marker (S-100), stem cell marker (Nestin), cytoskeletal proteins (GFAP and Vimentin), apoptotic pathway activation by Caspase-3 cleavage and cell viability, were evaluated. Surprisingly 20 min of exposure to continuous or amplitude modulated 900 MHz EMF induced a different and significant decrease in cell viability, some dynamic changes in the expression of the analysed markers and in the activation of the apoptotic pathway.