The role of β-catenin signaling pathway on proliferation of rats neural stem cells after hyperbaric oxygen therapy in vitro

Hyperbaric oxygen treatment increases intestinal stem cell proliferation through the mTORC1/S6K1 signaling pathway in Mus musculus

BACKGROUND

Hyperbaric oxygen treatment (HBOT) has been reported to modulate the proliferation of neural and mesenchymal stem cell populations, but the molecular mechanisms underlying these effects are not completely understood. In this study, we aimed to assess HBOT somatic stem cell modulation by evaluating the role of the mTOR complex 1 (mTORC1), a key regulator of cell metabolism whose activity is modified depending on oxygen levels, as a potential mediator of HBOT in murine intestinal stem cells (ISCs).

RESULTS

We discovered that acute HBOT synchronously increases the proliferation of ISCs without affecting the animal's oxidative metabolism through activation of the mTORC1/S6K1 axis. mTORC1 inhibition by rapamycin administration for 20 days also increases ISCs proliferation, generating a paradoxical response in mice intestines, and has been proposed to mimic a partial starvation state. Interestingly, the combination of HBOT and rapamycin does not have a synergic effect, possibly due to their differential impact on the mTORC1/S6K1 axis.

CONCLUSIONS

HBOT can induce an increase in ISCs proliferation along with other cell populations within the crypt through mTORC1/S6K1 modulation without altering the oxidative metabolism of the animal's small intestine. These results shed light on the molecular mechanisms underlying HBOT therapeutic action, laying the groundwork for future studies.

HBO Alleviates Neural Stem Cell Pyroptosis via lncRNA-H19/miR-423-5p/NLRP3 Axis and Improves Neurogenesis after Oxygen Glucose Deprivation

Due to the limited neurogenesis capacity, there has been a big challenge in better recovery from neurological dysfunction caused by stroke for a long time. Neural stem cell (NSC) programmed death is one of the unfavorable factors for neural regeneration after stroke. The types of death such as apoptosis and necroptosis have been deeply investigated while the pyroptosis of NSCs is not quite understood. Although it is well accepted that hyperbaric oxygen (HBO) alleviates the oxygen-glucose deprivation (OGD) injury after stroke and reduces programmed death of NSCs, whether NSC pyroptosis is involved in this process is still unknown. Therefore, this study is aimed at studying the potential effect of HBO treatment on NSC pyroptosis following OGD exposure, as well as its influence on NSC proliferation and differentiation in vitro. The results revealed that OGD increased NOD-like receptor protein 3 (NLRP3) expression to induce the pyroptotic death of NSCs, which was rescued by HBO treatment. And the upregulated lncRNA-H19 functioned as a molecular sponge of miR-423-5p to target NLRP3 for NSC pyroptosis following OGD. Most importantly, it was confirmed that HBO exerted protection of NSCs against pyroptosis by inhibiting lncRNA-H19/miR-423-5p/NLRP3 axis. Moreover, HBO restraint of lncRNA-H19-associated pyroptosis benefited the proliferation and neuronal differentiation of NSCs. It was concluded that HBO attenuated NSC pyroptosis via lncRNA-H19/miR-423-5p/NLRP3 axis and enhanced neurogenesis following OGD. The findings provide new insight into NSC programmed death and enlighten therapeutic strategy after stroke.

A review on the neuroprotective effects of hyperbaric oxygen therapy

Hyperbaric oxygen therapy, intermittent breathing of 100% oxygen at a pressure upper than sea level, has been shown to be some of the neuroprotective effects and used therapeutically in a wide range of neurological disorders. This review summarizes current knowledge about the neuroprotective effects of hyperbaric oxygen therapy with their molecular mechanisms in different models of neurological disorders.

Wnt/β-Catenin Signaling in Neural Stem Cell Homeostasis and Neurological Diseases

Neural stem/progenitor cells (NSCs) maintain the ability of self-renewal and differentiation and compose the complex nervous system. Wnt signaling is thought to control the balance of NSC proliferation and differentiation via the transcriptional coactivator β-catenin during brain development and adult tissue homeostasis. Disruption of Wnt signaling may result in developmental defects and neurological diseases. Here, we summarize recent findings of the roles of Wnt/β-catenin signaling components in NSC homeostasis for the regulation of functional brain circuits. We also suggest that the potential role of Wnt/β-catenin signaling might lead to new therapeutic strategies for neurological diseases, including, but not limited to, spinal cord injury, Alzheimer's disease, Parkinson's disease, and depression.

Vitamin A regulates neural stem cell proliferation in rats after hypoxic-ischemic brain damage via RARɑ-mediated modulation of the β-catenin pathway

Our previous experiments found that a suitable dose of vitamin A (VA) can affect neuronal apoptosis after hypoxic-ischemic brain damage (HIBD) by binding to RARα to activate the PI3K/AKT signaling pathway; however, the other neuroprotective effects of VA after HIBD, for example, whether it promotes neural stem cell (NSC) proliferation, remain unclear. In this study, in vivo and in vitro experiments revealed that VA regulates β-catenin signaling through RARɑ to affect NSC proliferation after HIBD and to improve neurocognitive outcomes. Because of the accumulation and suspended growth characteristics of NSCs, we performed in vitro experiments with PC12 cells to mimic NSCs. Flow cytometry, CCK8, EdU staining, immunofluorescence and behavioral tests were performed to explore the effects of retinoic acid (RA) on NSC proliferation and post-HIBD function. The expression of RARα and β-catenin pathway components were measured by real-time PCR and Western blotting. We found that the learning and memory of the VA-deficient (VAD) group was more seriously damaged than that of the VA normal (VAN) group. The proliferation of hippocampal NSCs was significantly decreased in the VAD group compared with the VAN group. The mRNA and protein expression of RARɑ, AKT, GSK-3β, β-catenin and Cyclin D1 were significantly lower in the VAD group than in the VAN group. In vitro, too high and too low of an RA intervention resulted in decreased proliferation, while an appropriate RA concentration (1-5 μmol/L) significantly promoted proliferation, S phase cells and high β-catenin pathway expression. These results suggested that VA can exert a neuroprotective effect by promoting the proliferation of hippocampal NSCs after neonatal HIBD injury at the appropriate concentration. VA activates RARɑ, which regulates the β-catenin signaling pathway, which in turn upregulates Cyclin D1 expression, promotes NSC proliferation, and finally plays a role in the neuroprotective effect.

Hyperbaric oxygen suppresses stemness-associated properties and Nanog and oncostatin M expression, but upregulates -catenin in orthotopic glioma models

Objective

This study aimed to explore whether initial hyperbaric oxygen treatment affects the stemness of glioma stem cells using an in vivo basal ganglia glioma model.

Methods

A basal ganglia glioma rat model was established. Rats were exposed to normal oxygen or hyperbaric oxygen on days 2, 4, 6, 8, 10, and 12. After 16 days of glioma cell inoculation, western blot, ELISA, and flow cytometry were performed to examine stemness-associated properties by examining the expression of CD133, A2B5, Nanog, oncostatin M, β-catenin, Oct-3/4, Sox2, and Nestin.

Results

Initial hyperbaric oxygen treatment began to affect glioma stemness-associated properties. The proportion of CD133⁺A2B5⁺ cells was significantly reduced after initial hyperbaric oxygen treatment. Additionally, the expression of stemness-related genes such as Nanog and oncostatin M was reduced, while TGF-β and β-catenin were increased.

Conclusions

Initial hyperbaric oxygen treatment not only alters the hypoxic microenvironment but also affects the stemness-associated properties of cancer stem cells.

Oligodendrocyte dysfunction and regeneration failure: A novel hypothesis of delayed encephalopathy after carbon monoxide poisoning

Carbon monoxide (CO) poisoning usually causes brain lesions and delayed encephalopathy, also known as delayed neurological sequelae (DNS). Demyelination of white matter (WM) is one of the most common sites of abnormalities in patients with DNS, but its mechanisms remain unclear. Oligodendrocytes (OLs) are myelinated cells that ensure the rapid conduction of neuronal axon signals and provide the nutritional factors necessary for maintaining nerve integrity in the central nervous system (CNS). OLs readily regenerate and replace damaged myelin membranes around axons in the adult mammalian CNS following demyelination. The ability to regenerate OLs depends on the availability of precursor cells (OPCs) in the CNS of adults. Multiple injury-related signals can induce OPC expansion followed by OL differentiation, axonal contact and myelin regeneration (remyelination). Therefore, OL dysfunction and regeneration failure in the deep WM of the brain are the key pathophysiological mechanisms leading to delayed brain injury after CO poisoning. CO-induced toxicity may interfere with OL function and render OPCs unable to regenerate OLs through some unclear mechanisms, leading to progressive demyelinating damage and resulting in DNS. In the future, combination therapies to reduce OL damage and promote OPC differentiation and remyelination may be important for the prevention and treatmentof DNS after CO poisoning.

The circular RNA ZNF292 alleviates OGD-induced injury in H9c2 cells via targeting BNIP3

The research aims to explore the roles and regulatory mechanisms of the circular RNA (circRNA) ZNF292 (circZNF292) in OGD-induced damage in H9c2 cells. The H9c2 cells were treated by OGD and/or transfected with circZNF292, si-circZNF292, pc-Bcl-2/adenovirus E1B-19 kDa-interacting protein 3 (BNIP3) or corresponding controls. Cell viability was detected with the CCK-8. The protein expression levels of the Bax, caspase-3, Beclin-1, p62, LC3, BNIP3, Wnt3a, β-catenin and mammalian target of rapamycin (mTOR) were individually determined via western blot. qRT-PCR was used to examine the circZNF292 expression level. The apoptotic rate was determined by the Annexin V-FITC/PI with flow cytometer. The production of the circZNF292 was promoted by OGD. Abundant circZNF292 released OGD-induced damage by up-regulating cell viability and Wnt3a/β-catenin or mTOR proteins, but down-regulating apoptosis and autophagy. circZNF292 had an opposite effect on these elements mentioned above. Besides, BNIP3 was negatively adjusted by the circZNF292. The BNIP3 overproduction destroyed the protective effect of circZNF292 on H9c2. circZNF292 released OGD-induced damage in the H9c2 cells by targeting the BNIP3 through Wnt/β-catenin and mTOR activation.

HBO Promotes the Differentiation of Neural Stem Cells via Interactions Between the Wnt3/β-Catenin and BMP2 Signaling Pathways

Hyperbaric oxygen (HBO) therapy may promote neurological recovery from hypoxic-ischemic encephalopathy (HIE). However, the therapeutic effects of HBO and its associated mechanisms remain unknown. The canonical Wnt/β-catenin signaling pathways and bone morphogenetic protein (BMP) play important roles in mammalian nervous system development. The present study examined whether HBO stimulates the differentiation of neural stem cells (NSCs) and its effect on Wnt3/β-catenin and BMP2 signaling pathways. We showed HBO treatment (2 ATA, 60 min) promoted differentiation of NSCs into neurons and oligodendrocytes in vitro. In addition, rat hypoxic-ischemic brain damage (HIBD) tissue extracts also promoted the differentiation of NSCs into neurons and oligodendrocytes, with the advantage of reducing the number of astrocytes. These effects were most pronounced when these two were combined together. In addition, the expression of Wnt3a, BMP2, and β-catenin nuclear proteins were increased after HBO treatment. However, blockade of Wnt/β-catenin or BMP signaling inhibited NSC differentiation and reduced the expression of Wnt3a, BMP2, and β-catenin nuclear proteins. In conclusion, HBO promotes differentiation of NSCs into neurons and oligodendrocytes and reduced the number of astrocytes in vitro possibly through regulation of Wnt3/β-catenin and BMP2 signaling pathways. HBO may serve as a potential therapeutic strategy for treating HIE.

Priming of the Cells: Hypoxic Preconditioning for Stem Cell Therapy

Objective:

Stem cell-based therapies are promising in regenerative medicine for protecting and repairing damaged brain tissues after injury or in the context of chronic diseases. Hypoxia can induce physiological and pathological responses. A hypoxic insult might act as a double-edged sword, it induces cell death and brain damage, but on the other hand, sublethal hypoxia can trigger an adaptation response called hypoxic preconditioning or hypoxic tolerance that is of immense importance for the survival of cells and tissues.

Data Sources:

This review was based on articles published in PubMed databases up to August 16, 2017, with the following keywords: “stem cells,” “hypoxic preconditioning,” “ischemic preconditioning,” and “cell transplantation.”

Study Selection:

Original articles and critical reviews on the topics were selected.

Results:

Hypoxic preconditioning has been investigated as a primary endogenous protective mechanism and possible treatment against ischemic injuries. Many cellular and molecular mechanisms underlying the protective effects of hypoxic preconditioning have been identified.

Conclusions:

In cell transplantation therapy, hypoxic pretreatment of stem cells and neural progenitors markedly increases the survival and regenerative capabilities of these cells in the host environment, leading to enhanced therapeutic effects in various disease models. Regenerative treatments can mobilize endogenous stem cells for neurogenesis and angiogenesis in the adult brain. Furthermore, transplantation of stem cells/neural progenitors achieves therapeutic benefits via cell replacement and/or increased trophic support. Combinatorial approaches of cell-based therapy with additional strategies such as neuroprotective protocols, anti-inflammatory treatment, and rehabilitation therapy can significantly improve therapeutic benefits. In this review, we will discuss the recent progress regarding cell types and applications in regenerative medicine as well as future applications.

Nitrous Oxide Induces Prominent Cell Proliferation in Adult Rat Hippocampal Dentate Gyrus

The identification of distinct and more efficacious antidepressant treatments is highly needed. Nitrous oxide (N₂O) is an N-methyl-D-aspartic acid (NMDA) antagonist that has been reported to exhibit antidepressant effects in treatment-resistant depression (TRD) patients. Yet, no studies have investigated the effects of sub-anesthetic dosages of N₂O on hippocampal cell proliferation and neurogenesis in adult brain rats. In our study, adult male Sprague-Dawley rats were exposed to single or multiple exposures to mixtures of 70% N₂O and 30% oxygen (O₂). Sham groups were exposed to 30% O₂ and the control groups to atmospheric air. Hippocampal cell proliferation was assessed by bromodeoxyuridine (BrdU) incorporation, and BrdU-positive cells were counted in the dentate gyrus (DG) using confocal microscopy. Results showed that while the rates of hippocampal cell proliferation were comparable between the N₂O and sham groups at day 1, levels increased by 1.4 folds at day 7 after one session exposure to N₂O. Multiple N₂O exposures significantly increased the rate of hippocampal cell proliferation to two folds. Therefore, sub-anesthetic doses of N₂O, similar to ketamine, increase hippocampal cell proliferation, suggesting that there will ultimately be an increase in neurogenesis. Future studies should investigate added N₂O exposures and their antidepressant behavioral correlates.

Impact of siRNA targeting of β-catenin on differentiation of rat neural stem cells and gene expression of Ngn1 and BMP4 following in vitro hypoxic-ischemic brain damage

The aim of the present study was to investigate the possible damage-repair mechanisms of neural stem cells (NSCs) following hypoxic-ischemic brain damage (HIBD). NSCs obtained from Sprague Dawley rats were treated with tissue homogenate from normal or HIBD tissue, and β-catenin expression was silenced using siRNA. The differentiation of NSCs was observed by immunofluorescence, and semiquantitative reverse transcription-polymerase chain reaction and western blot analysis were applied to detect the mRNA and protein expression levels of Ngn1 and BMP4 in the NSCs. Compared with control NSCs, culture with brain tissue homogenate significantly increased the differentiation of NSCs into neurons and oligodendrocytes (P<0.05), whereas differentiation into astrocytes was significantly reduced (P<0.05). Compared with negative control-transfected cells, knockdown of β-catenin expression significantly decreased the differentiation of NSCs into neurons and oligodendrocytes (P<0.01), whereas the percentage of NSCs differentiated into astrocytes was significantly increased (P<0.01). Compared with control NSCs, the mRNA and protein expression levels of Ngn1 were significantly increased (P<0.01) and BMP4 levels were significantly reduced (P<0.01) by exposure of the cells to brain tissue homogenate. Compared with the negative control plasmid-transfected NSCs, the levels of Ngn1 mRNA and protein were significantly reduced by β-catenin siRNA (P<0.01), whereas BMP4 levels were significantly increased (P<0.01). In summary, the damaged brain tissues in HIBD may promote NSCs to differentiate into neurons for self-repair processes. β-Catenin, BMP4 and Ngn1 may be important for the coordination of NSC proliferation and differentiation following HIBD.

Alterations in taste perception as a result of hyperbaric oxygen therapy

The present study evaluates the effect of hyperbaric oxygen therapy on taste sensitivity, hedonic perception of taste, and food preferences. The studied groups included 197 people in total (79 in the study group; 118 in the control group). All patients from the study group were treated with hyperbaric oxygen therapy due to chronic non-healing wounds. The control group consisted of healthy people, who did not receive hyperbaric oxygen therapy. The taste intensity, recognition thresholds, and hedonic perception were examined using gustatory tests. The aqueous solutions of sucrose for sweet, sodium chloride for salty, citric acid for sour, quinine hydrochloride for bitter, and monosodium glutamate for umami taste were used. The participants fulfilled the questionnaire to examine pleasure derived from eating certain types of dishes. Gustatory tests and analyses of the pleasure derived from eating in the study group were carried out before the first exposure to hyperbaric oxygen and then at the end of therapy, after at least 25 sessions of treatment. In the control group, examination of perception of taste sensations was conducted only once. The results of comparing patients with non-healing wounds with healthy people are characterized by reduced taste sensitivity. After participation in hyperbaric oxygen therapy, the improvement in perception of taste sensations and changes in hedonic evaluation have occurred among patients with non-healing wounds. In terms of food preference, a decreased desire for eating sweet desserts, chocolate, and crisps was observed in those patients who received hyperbaric oxygen therapy.

Vanillin and 4-hydroxybenzyl alcohol promotes cell proliferation and neuroblast differentiation in the dentate gyrus of mice via the increase of brain-derived neurotrophic factor and tropomyosin-related kinase B

4-Hydroxy-3-methoxybenzaldehyde (vanillin) and 4-hydroxybenzyl alcohol (4-HBA) are well-known phenolic compounds, which possess various therapeutic properties and are widely found in a variety of plants. In the present study, the effects of vanillin and 4-HBA were first investigated on cell proliferation, as well as neuronal differentiation and integration of granule cells in the dentate gyrus (DG) of adolescent mice using Ki-67, doublecortin (DCX) immunohistochemistry and 5-bromo-2′-de-oxyuridine (BrdU)/feminizing Locus on X 3 (NeuN) double immunofluorescence. In both the vanillin and 4-HBA groups, the number of Ki-67⁺ cells, DCX⁺ neuroblasts and BrdU⁺/NeuN⁺ neurons were significantly increased in the subgranular zone of the DG, as compared with the vehicle group. In addition, the levels of brain-derived neurotrophic factor (BDNF) and tropomyosin-related kinase B (TrkB), a BDNF receptor, were significantly increased in the DG in the vanillin and 4-HBA groups compared with the vehicle group. These results indicated that vanillin and 4-HBA enhanced cell proliferation, neuroblast differentiation and integration of granule cells in the DG of adolescent mice. These neurogenic effects of vanillin and 4-HBA may be closely associated with increases in BDNF and TrkB.

Current Neurogenic and Neuroprotective Strategies to Prevent and Treat Neurodegenerative and Neuropsychiatric Disorders

The adult central nervous system is commonly known to have a very limited regenerative capacity. The presence of functional stem cells in the brain can therefore be seen as a paradox, since in other organs these are known to counterbalance cell loss derived from pathological conditions. This fact has therefore raised the possibility to stimulate neural stem cell differentiation and proliferation or survival by either stem cell replacement therapy or direct administration of neurotrophic factors or other proneurogenic molecules, which in turn has also originated regenerative medicine for the treatment of otherwise incurable neurodegenerative and neuropsychiatric disorders that take a huge toll on society. This may be facilitated by the fact that many of these disorders converge on similar pathophysiological pathways: excitotoxicity, oxidative stress, neuroinflammation, mitochondrial failure, excessive intracellular calcium and apoptosis. This review will therefore focus on the most promising achievements in promoting neuroprotection and neuroregeneration reported to date.

Hyperbaric oxygen, vasculogenic stem cells, and wound healing

SIGNIFICANCE

Oxidative stress is recognized as playing a role in stem cell mobilization from peripheral sites and also cell function.

RECENT ADVANCES

This review focuses on the impact of hyperoxia on vasculogenic stem cells and elements of wound healing.

CRITICAL ISSUES

Components of the wound-healing process in which oxidative stress has a positive impact on the various cells involved in wound healing are highlighted. A slightly different view of wound-healing physiology is adopted by departing from the often used notion of sequential stages: hemostatic, inflammatory, proliferative, and remodeling and instead organizes the cascade of wound healing as overlapping events or waves pertaining to reactive oxygen species, lactate, and nitric oxide. This was done because hyperoxia has effects of a number of cell signaling events that converge to influence cell recruitment/chemotaxis and gene regulation/protein synthesis responses which mediate wound healing.

FUTURE DIRECTIONS

Our alternative perspective of the stages of wound healing eases recognition of the multiple sites where oxidative stress has an impact on wound healing. This aids the focus on mechanistic events and the interplay among various cell types and biochemical processes. It also highlights the areas where additional research is needed.

CD34+/CD45-dim stem cell mobilization by hyperbaric oxygen - changes with oxygen dosage

Because hyperbaric oxygen treatment mobilizes bone marrow derived-stem/progenitor cells by a free radical mediated mechanism, we hypothesized that there may be differences in mobilization efficiency based on exposure to different oxygen partial pressures. Blood from twenty consecutive patients was obtained before and after the 1st, 10th and 20th treatment at two clinical centers using protocols involving exposures to oxygen at either 2.0 or 2.5 atmospheres absolute (ATA). Post-treatment values of CD34+, CD45-dim leukocytes were always 2-fold greater than the pre-treatment values for both protocols. Values for those treated at 2.5 ATA were significantly greater than those treated at 2.0 ATA by factors of 1.9 to 3-fold after the 10th and before and after the 20th treatments. Intracellular content of hypoxia inducible factors -1, -2, and -3, thioredoxin-1 and poly-ADP-ribose polymerase assessed in permeabilized CD34+ cells with fluorophore-conjugated antibodies were twice as high in all post- versus pre-treatment samples with no significant differences between 2.0 and 2.5 ATA protocols. We conclude that putative progenitor cell mobilization is higher with 2.5 versus 2.0 ATA treatments, and all newly mobilized cells exhibit higher concentrations of an array of regulatory proteins.

Umbilical cord blood cells regulate the differentiation of endogenous neural stem cells in hypoxic ischemic neonatal rats via the hedgehog signaling pathway

Transplantation of umbilical cord blood mononuclear cells (UCBMC) promotes the proliferation of endogenous neural stem cells (NSCs), but it has been unclear whether the proliferating NSCs can differentiate into mature neural cells. Therefore, we explored the effects of UCBMC transplantation on the differentiation of endogenous NSCs and their underlying mechanisms. Seven-day-old Sprague-Dawley rats underwent left carotid ligation followed by hypoxic stress. UCBMC were transplanted 24h after hypoxia ischemia (HI). BrdU/β-tubulin/HNA/DAPI, BrdU/GFAP/HNA/DAPI, Ngn1/DAPI, and BMP4/DAPI were measured by immunofluorescence staining; Shh, Gli1, Ngn1, and BMP4 proteins were measured by western-blot analysis 28 days after transplantation. More newborn neurons and fewer astrocytes were observed in the HI+UCBMC group, its neuronal percentage was higher, and glial percentage was lower compared with the N+UCBMC (P<0.05) and HI+PBS groups (P<0.01), while fewer newborn neurons and more newborn astrocytes were found in the HI+cyclopamine (an antagonist of the hedgehog protein)+UCBMC group compared with the HI+UCBMC group (P<0.01). The expression of Shh, Gli1, and Ngn1 proteins was higher and BMP4 protein was lower in the HI+UCBMC compared with the HI+PBS group (P<0.01) and the HI+cyclopamine+UCBMC group (P<0.01). Linear regression analysis showed that the differentiation of NSCs correlated with expression of Ngn1 and BMP4 proteins (P<0.01). In conclusion, UCBMC promote neuronal differentiation and reduce glial differentiation in hypoxic ischemic neonatal rats via the hedgehog signaling pathway.

Serum leptin levels decrease after permanent MCAo in the rat and remain unaffected by delayed hyperbaric oxygen therapy

Hyperbaric oxygen therapy (HBOT), referring to the medical use of oxygen at a level higher than atmospheric pressure, exerts neuroprotective effects after ischemic stroke via various mechanisms. It has been demonstrated that HBOT modulates the synthesis and degradation of hormones. Leptin, an adipose derived hormone, has been found to confer neuroprotection following experimental stroke. However, it is not known whether HBOT alters leptin concentrations after permanent middle cerebral artery occlusion (pMCAo) in the rat. In this present study, we aimed to investigate the effect of HBOT on the serum concentration of leptin in rats subjected to pMCAo. HBOT was initiated 48 hrs after experimental pMCAo, at 2.5 atmospheres absolutes with 100% oxygen, 1 hr a day for 10 consecutive days. Body weight, neurobehavioral deficits and infarct size were evaluated. Blood was collected on day 1 and day 16 following HBOT. Serum leptin concentrations were measured with ELISA. Delayed HBOT reduced infarct size and improved neurobehavioral scores. Decreased serum levels of leptin were found in treated and untreated pMCAo animals, compared to the sham group on day 1 (P > 0.05) and day 16 (P < 0.05). However, no statistical significance was found between HBOT and the air group. We concluded that the neuroprotective effects of delayed HBOT in pMCAo rats were unlikely to be exerted through changes in the serum concentration of leptin.

Wnt signaling: role in Alzheimer disease and schizophrenia

Wnt signaling function starts during the development of the nervous system and is crucial for synaptic plasticity in the adult brain. Clearly Wnt effects in synaptic and plastic processes are relevant, however the implication of this pathway in the prevention of neurodegenerative diseases that produce synaptic impairment, is even more interesting. Several years ago our laboratory found a relationship between the loss of Wnt signaling and the neurotoxicity of the amyloid-β-peptide (Aβ), one of the main players in Alzheimer's disease (AD). Moreover, the activation of the Wnt signaling cascade prevents Aβ-dependent cytotoxic effects. In fact, disrupted Wnt signaling may be a direct link between Aβ-toxicity and tau hyperphosphorylation, ultimately leading to impaired synaptic plasticity and/or neuronal degeneration, indicating that a single pathway can account for both neuro-pathological lesions and altered synaptic function. These observations, suggest that a sustained loss of Wnt signaling function may be a key relevant factor in the pathology of AD. On the other hand, Schizophrenia remains one of the most debilitating and intractable illness in psychiatry. Since Wnt signaling is important in organizing the developing brain, it is reasonable to propose that defects in Wnt signaling could contribute to Schizophrenia, particularly since the neuro-developmental hypothesis of the disease implies subtle dys-regulation of brain development, including some core components of the Wnt signaling pathways such as GSK-3β or Disrupted in Schizophrenia-1 (DISC-1). This review focuses on the relationship between Wnt signaling and its potential relevance for the treatment of neurodegenerative and neuropsychiatric diseases including AD and Schizophrenia.

Prenatal exposure to valproic acid increases the neural progenitor cell pool and induces macrocephaly in rat brain via a mechanism involving the GSK-3β/β-catenin pathway

Autism is a spectrum of neurodevelopmental disorders characterized by social isolation and lack of interaction. Anatomically, autism patients often show macrocephaly and high neuronal density. To investigate the mechanism underlying the higher neuronal populations seen in ASD, we subcutaneously injected VPA (400 mg/kg) into pregnant Sprague-Dawley rats on E12, an animal model often used in ASD study. Alternatively, cultured rat neural progenitor cells were treated with VPA. Until E18, VPA induced NPC proliferation and delayed neurogenesis in fetal brain, but the subsequent differentiation of NPCs to neurons increased brain neuronal density afterward. Similar findings were observed with NPCs treated with VPA in vitro. At a molecular level, VPA enhanced Wnt1 expression and activated the GSK-3β/β-catenin pathway. Furthermore, inhibition of this pathway attenuated the effects of VPA. The findings of this study suggest that an altered developmental process underlies the macrocephaly and abnormal brain structure observed in the autistic brain.

Hyperbaric oxygen therapy promotes neurogenesis: where do we stand?

Neurogenesis in adults, initiated by injury to the central nervous system (CNS) presents an autologous repair mechanism. It has been suggested that hyperbaric oxygen therapy (HBOT) enhances neurogenesis which accordingly may improve functional outcome after CNS injury. In this present article we aim to review experimental as well as clinical studies on the subject of HBOT and neurogenesis. We demonstrate hypothetical mechanism of HBOT on cellular transcription factors including hypoxia-inducible factors (HIFs) and cAMP response element binding (CREB). We furthermore reveal the discrepancy between experimental findings and clinical trials in regards of HBOT. Further translational preclinical studies followed by improved clinical trials are needed to elucidate potential benefits of HBOT.