José Joaquín Merino

Cerebral Protection, Brain Repair, Plasticity and Cell Therapy in Ischemic Stroke

Among available treatments in the acute ischemic stroke, only intravenous thrombolysis has been demonstrated to be efficacious. Although the majority of pharmacological neuroprotectants have been efficacious in experimental studies, they have failed in clinical trials. Hence, we need to consider integrated cerebral protection which includes the concept of cerebral repair by supporting cerebral plasticity. We provide a nonsystematic review of the studies published on cerebral protection and repair treatments of cerebral ischemia considering the possibilities of stimulating brain plasticity by trophic factors and cell therapy. The majority of the neuroprotective drugs have failed in clinical trials. Citicoline shows a benefit in meta-analysis and it is currently being explored in a new trial (ICTUS). Neuroprotective drugs combined with reperfusion offer favorable results in experimental animals, but data from clinical studies are not enough. Repair therapies using cerebral plasticity stimulation (trophic factors) and cell therapy have shown certain efficacy in experimental and clinical studies and they are a developing route with clinical therapeutic perspectives.

CXCR4/CXCR7 Molecular Involvement in Neuronal and Neural Progenitor Migration: Focus in CNS Repair

In the adult brain, neural progenitor cells (NPCs) reside in the subventricular zone (SVZ) of the lateral ventricles, the dentate gyrus and the olfactory bulb. Following CNS insult, NPCs from the SVZ can migrate along the rostral migratory stream (RMS), a migration of NPCs that is directed by proinflammatory cytokines. Cells expressing CXCR4 follow a homing signal that ultimately leads to neuronal integration and CNS repair, although such molecules can also promote NPC quiescence. The ligand, SDF1 alpha (or CXCL12) is one of the chemokines secreted at sites of injury that it is known to attract NSC‐derived neuroblasts, cells that express CXCR4. In function of its concentration, CXCL12 can induce different responses, promoting NPC migration at low concentrations while favoring cell adhesion via EGF and the alpha 6 integrin at high CXCL12 concentrations. However, the preclinical effectiveness of chemokines and their relationship with NPC mobilization requires further study, particularly with respect to CNS repair. NPC migration may also be affected by the release of cytokines or chemokines induced by local inflammation, through autocrine or paracrine mechanisms, as well as through erythropoietin (EPO) or nitric oxide (NO) release. CXCL12 activity requires G‐coupled proteins and the availability of its ligand may be modulated by its binding to CXCR7, for which it shows a stronger affinity than for CXCR4. J. Cell. Physiol. 230: 27–42, 2015.

Silicon as neuroprotector or neurotoxic in the human neuroblastoma SH-SY5Y cell line.

Silicon (Si) is a trace element that has been considered to be an environmental contaminant for many years, although different studies have recently reported it is an essential element for living cells. The present study tested the ability of different concentrations of Si G57™ to induce neuroprotection or neurotoxicity over 24 h in the SH-SY5Y human neuroblastoma cell line. Cell viability, cellular proliferation, LDH release, ROS, antioxidant capacity, TBARS, caspase-3, -8 and -9, DNA fragmentation, and TNF-α levels were evaluated. Low Si doses (50-250 ng mL(-1)) increased the cell viability and reduced caspase-3 and -8 activities and TNF-α level. The increase in cell viability was independent of any proliferative effect as there was no variation in cyclin E and PCNA levels. At higher concentrations, Si increased caspase-3, as well as TBARS, LDH, DNA fragmentation, and TNF-α releases. Altogether, these results suggest that Si could act either as a neuroprotector or a neurotoxic agent depending on the concentration tested. This study emphasizes the importance of developing new neuroprotective therapies based on low Si doses.

CXCR4/SDF-1α-Chemokine Regulates Neurogenesis and/or Angiogenesis within the Vascular Niche of Ischemic Rats; However, does SDF-1α Play a Role in Repair?

Ischemic stroke is an important complication of atrial fibrillation (AF) and risk stratification schemes that predict thromboembolic events in patients with AF are important for indicating antithrombotic therapy in order to prevent stroke occurrence (1). The CHA2DS2VASc score (2) is the most complete stratification scheme, which was recently recommended by the European Society of Cardiology (1). Another score scheme, the CHADS2 (3) is easy to apply and widely used but may not be as efficacious. Of 215 patients admitted with ischemic stroke at the emergency department of Hospital Israelita Albert Einstein (a tertiary hospital in São Paulo, Brazil) between September 2004 and March 2006, we found 35 patients with AF and ischemic stroke. We then applied parameters previous to stroke admission to these 35 patients using the CHADS2 and CHA2DS2-VASc scores. Nine of the 35 patients scored one in CHADS2 score (25 5%), and were reassessed by CHA2DS2-VASc score; two had CHA2DS2-VASc score of two; five had CHA2DS2-VASc score of three, and two had CHA2DS2-VASc score of four. Factors that increased scoring were: having an age range of 65–74, age Z75 years, female gender, and coronary artery disease. These factors are associated to increased riskof ischemic stroke in patients with AF (4, 5) and are not considered in CHADS2. Accordingly, we also had a statistically significant increase in AF prevalence in older patients, mainly 80 years or older (Po0 01, Fisher exact test, significance level 5%) vs. younger patients. All patients with a CHADS2 score of one were not under anticoagulation but in retrospect had CHA2DS2-VASc score Z2, which indicated the need for oral anticoagulation. Risk stratification using CHA2DS2VASc score would have optimized indication for oral anticoagulation in our patients and hence reduced their risk of stroke. We recommend the complementation of risk stratification by applying CHA2DS2-VASc score in all patients with CHADS2 scores of zero and one.

Antioxidant and protective mechanisms against hypoxia and hypoglycaemia in cortical neurons in vitro.

In the present work, we have studied whether cell death could be induced in cortical neurons from rats subjected to different period of O2 deprivation and low glucose (ODLG). This “in vitro” model is designed to emulate the penumbra area under ischemia. In these conditions, cortical neurons displayed loss of mitochondrial respiratory ability however, nor necrosis neither apoptosis occurred despite ROS production. The absence of cellular death could be a consequence of increased antioxidant responses such as superoxide dismutase-1 (SOD1) and GPX3. In addition, the levels of reduced glutathione were augmented and HIF-1/3α overexpressed. After long periods of ODLG (12–24 h) cortical neurons showed cellular and mitochondrial membrane alterations and did not recuperate cellular viability during reperfusion. This could mean that therapies directed toward prevention of cellular and mitochondrial membrane imbalance or cell death through mechanisms other than necrosis or apoptosis, like authophagy, may be a way to prevent ODLG damage.

The Nitric Oxide Donor SNAP-Induced Amino Acid Neurotransmitter Release in Cortical Neurons. Effects of Blockers of Voltage-Dependent Sodium and Calcium Channels

Background The discovery that nitric oxide (NO) functions as a signalling molecule in the nervous system has radically changed the concept of neuronal communication. NO induces the release of amino acid neurotransmitters but the underlying mechanisms remain to be elucidated. Findings The aim of this work was to study the effect of NO on amino acid neurotransmitter release (Asp, Glu, Gly and GABA) in cortical neurons as well as the mechanism underlying the release of these neurotransmitters. Cortical neurons were stimulated with SNAP, a NO donor, and the release of different amino acid neurotransmitters was measured by HPLC. The involvement of voltage dependent Na+ and Ca2+ channels as well as cGMP in its mechanism of action was evaluated. Conclusions Our results indicate that NO induces release of aspartate, glutamate, glycine and GABA in cortical neurons and that this release is inhibited by ODQ, an inhibitor of soluble guanylate cyclase. Thus, the NO effect on amino acid neurotransmission could be mediated by cGMP formation in cortical neurons. Our data also demonstrate that the Na+ and Ca2+ voltage- dependent calcium channels are involved in the NO effects on cortical neurons.

Zirconia implants and peek restorations for the replacement of upper molars

BackgroundOne of the disadvantages of the zirconia implants is the lack of elasticity, which is increased with the use of ceramic or zirconia crowns. The consequences that could result from this lack of elasticity have led to the search for new materials with improved mechanical properties.Case presentationA patient who is a 45-year-old woman, non-smoker and has no medical record of interest with a longitudinal fracture in the palatal root of molar tooth 1.7 and absence of tooth 1.6 was selected in order to receive a zirconia implant with a PEEK-based restoration and a composite coating. The following case report describes and analyses treatment with zirconia implants in molars following a flapless surgical technique. Zirconia implants are an alternative to titanium implants in patients with allergies or who are sensitive to metal alloys. However, one of the disadvantages that they have is their lack of elasticity, which increases with the use of ceramic or zirconia crowns. The consequences that can arise from this lack of elasticity have led to the search for new materials with better mechanical properties to cushion occlusal loads. PEEK-based restoration in implant prosthetics can compensate these occlusal forces, facilitating cushioning while chewing.ConclusionThis procedure provides excellent elasticity and resembles natural tooth structure. This clinical case suggests that PEEK restorations can be used in zirconia implants in dentistry.

The CXCR7 activation by SDF1 induces Neural progenitor migration (NPC): a dual effect on CXCR4/CXCR7 axis within the vascular niche of ischemic rats

Dear Editor, there is a certain controversy about the protective role of SDF1 Alpha in the pathophysiology of cerebral ischemia and its interaction with CXCR4 and CXCR7 Alpha chemokine receptors. Can SDF1 Alpha induce neuroprotective or neurotoxic events in the vascular niche of ischemia rats? Huang et al. 2012 recently published that AMD3100, a CXCR4 antagonist, reduced cytokine release in the ischemic cortex as well as induced blood–brain barrier dysfunction after middle cerebral artery occlusion when the drug was administered at a dose of 1 mg/kg for three-days after ischemia, i.p (1). However, their study did not consider whether SDF1 Alpha = CXCL12 could activate CXCR7 chemokine receptor as CXCL12 has 10 times more affinity for CXCR7 than it does for CXCR4 but does not signal through G coupled proteins, in contraposition to CXCR4. Thus, part of the AMD3100 protective effects reported by Huang et al. 2013 could be due to CXCR7 activation, since AMD3100 is an inverse agonist for CXCR7. Another recent study published in Plos One by Ramos Cejudo et al., 2012 described a reduced mRNA CXCR4 expression after ischemia in the perinfarct area, as compared with the core (3). These findings are in contraposition with the ‘reparative’ role report by CXCR4/SDF1 Alpha within the vascular niche (2). The study by Ramos Cejudo et al., 2012 detecting CXCR4 donwregulation argued that chemokines induce stem cell trafficking (3). CXCR4/SDF1 Alpha are cue factors that promote neurogenesis and angiogenesis within the vascular niche in cerebral ischemia (4). In addition, AMD3100 reduces Myeloperoxidase (MPO) activity in AMD3100-treated ischemic rats (1). However, we must not underconsider the role of CXCR7 activation by SDF1 Alpha = CXCR7 because this ligand induces NPC migration within the periinfarct area because AMD3100 can also act as an inverse agonist for CXCR7 (2). Moreover, CXCR7 signaling attenuates the adaptative cellular response to acute SDF1 Alpha stimulation (≤12 h) after hypoxia (5). Thus, part of the protective effects reported by Huang could be attributed to AMD3100 acting as an inverse agonist for CXCR7 (2). Interestingly, CXCL12 increases human neural progenitor cell survival through a CXCR7and CXCR4-mediated endocytotic mechanism (6). In addition, can microarrays for the CXCR4/SDF1 Alpha axis really detect functional chemokine receptor activation within the periinfarct area in the Ramos Cejudo’s study? CXCR4/CXCR7/SDF1 Alpha can be located on neurons and glial cells. Thus, the Ramos Cejudo et al., 2012 study report that CXCR4 downregulation does not distinguish between neuronal or glial CXCR4 expression. In addition, CXCR4/CXCR7 undergoes posttranslational modifications (ubiquitinization or dimerization), which cannot be detected by microarrays. Moreover, their study does not address the question of whether CXCR4 changes might be regulated differentially by either neurons or glial cells. We think that the reported CXCR4 downregulation is no more than a consequence of compensatory CXCR4 changes between neuronal and glial responses as microarrays cannot distinguish between the percentages that belong to either cell type in the Ramos-Cejudo study. This distinction is crucial for understanding the neurotoxic cascade within the vascular niche in cerebral ischemia. In our opinion, these two aspects must be studied and differentiated in the perinfarct area because CXCR7 activation promotes antiapoptotic and proliferation effects in Neural Progenitor cells (NPC).

Increased Zn/Glutathione Levels and Higher Superoxide Dismutase-1 Activity as Biomarkers of Oxidative Stress in Women with Long-Term Dental Amalgam Fillings: Correlation between Mercury/Aluminium Levels (in Hair) and Antioxidant Systems in Plasma.

55 hair samples (42 females with amalgam fillings and 13 female control subjects) were obtained. All subjects (mean age 44 years) who had dental amalgam filling for more than 10 years (average 15 years). Certain metals were quantified by ICP-MS (Mass Spectrophotometry) in hair (μg/g: Al, Hg, Ba, Ag, Sb, As, Be, Bi, Cd, Pb, Pt, Tl, Th, U, Ni, Sn, Ti) and SOD-1 and Glutathione (reduced form) levels in plasma. Data were compared with controls without amalgams, and analyzed to identify any significant relation between metals and the total number of amalgam fillings, comparing those with four or less (n = 27) with those with

The Impact of CXCR4 Blockade on the Survival of Rat Brain Cortical Neurons.

Background: Chemokine receptor type 4 (CXCR4) plays a role in neuronal survival/cell repair and also contributes to the progression of cancer and neurodegenerative diseases. Chemokine ligand 12 (CXCL12) binds to CXCR4. In this study, we have investigated whether CXCR4 blockade by AMD3100 (a CXCR4 antagonist, member of bicyclam family) may affect neuronal survival in the absence of insult. Thus, we have measured the mitochondrial membrane potential (MMP), Bax and Bcl-2 protein translocation, and cytochrome c release in AMD3100-treated brain cortical neurons at 7 DIV (days in vitro). Methods: For this aim, AMD3100 (200 nM) was added to cortical neurons for 24 h, and several biomarkers like cell viability, reactive oxygen species (ROS) generation, lactate dehydrogenase (LDH) release, caspase-3/9 activity, proteins Bax and Bcl-2 translocation, and cytochrome c release were analyzed by immunoblot. Results: CXCR4 blockade by AMD3100 (200 nM, 24 h) induces mitochondrial hyperpolarization and increases caspase-3/9 hyperpolarization without affecting LDH release as compared to untreated controls. AMD3100 also increases cytochrome c release and promotes Bax translocation to the mitochondria, whereas it raises cytosolic Bcl-2 levels in brain cortical neurons. Conclusion: CXCR4 blockade induces cellular death via intrinsic apoptosis in rat brain cortical neurons in absence of insult.