Metabolic disorders exacerbate the formation of glial scar after stroke.

Metabolic disorders are risk factors for stroke exacerbating subsequent complications. Rapidly after brain injury, a glial scar forms, preventing excessive inflammation and limiting axonal regeneration. Despite the growing interest in wound healing following brain injury, the formation of a glial scar in the context of metabolic disorders is poorly documented. In this study, we used db/db mice to investigate the impact of metabolic perturbations on brain repair mechanisms, with a focus on glial scarring. First, we confirmed the development of obesity, poor glucose regulation, hyperglycaemia and liver steatosis in these mice. Then, we observed that 3 days after a 30-min middle cerebral artery occlusion (MCAO), db/db mice had larger infarct area compared with their control counterparts. We next investigated reactive gliosis and glial scar formation in db/+ and db/db mice. We demonstrated that astrogliosis and microgliosis were exacerbated 3 days after stroke in db/db mice. Furthermore, we also showed that the synthesis of extracellular matrix (ECM) proteins (i.e., chondroitin sulphate proteoglycan, collagen IV and tenascin C) was increased in db/db mice. Consequently, we demonstrated for the first time that metabolic disorders impair reactive gliosis post-stroke and increase ECM deposition. Given that the damage size is known to influence glial scar, this study now raises the question of the direct impact of hyperglycaemia/obesity on reactive gliosis and glia scar. It paves the way to promote the development of new therapies targeting glial scar formation to improve functional recovery after stroke in the context of metabolic disorders.

Secret talk between adipose tissue and central nervous system via secreted factors-an emerging frontier in the neurodegenerative research.

First seen as a storage organ, the white adipose tissue (WAT) is now considered as an endocrine organ. WAT can produce an array of bioactive factors known as adipokines acting at physiological level and playing a vital role in energy metabolism as well as in immune response. The global effect of adipokines in metabolic activities is well established, but their impact on the physiology and the pathophysiology of the central nervous system (CNS) remains poorly defined. Adipokines are not only produced by the WAT but can also be expressed in the CNS where receptors for these factors are present. When produced in periphery and to affect the CNS, these factors may either cross the blood brain barrier (BBB) or modify the BBB physiology by acting on cells forming the BBB. Adipokines could regulate neuroinflammation and oxidative stress which are two major physiological processes involved in neurodegeneration and are associated with many chronic neurodegenerative diseases. In this review, we focus on four important adipokines (leptin, resistin, adiponectin, and TNFα) and one lipokine (lysophosphatidic acid-LPA) associated with autotaxin, its producing enzyme. Their potential effects on neurodegeneration and brain repair (neurogenesis) will be discussed. Understanding and regulating these adipokines could be an interesting lead to novel therapeutic strategy in order to counteract neurodegenerative disorders and/or promote brain repair.

New insights into lidocaine and adrenaline effects on human adipose stem cells.

BACKGROUND: Adipose stem cells have gained great interest in plastic and reconstructive surgery with their ability to improve engraftment after fat transfer for soft tissue filling. It is therefore essential to know the effect of the drugs commonly used during the lipoaspiration procedure, such as lidocaine and adrenaline. Indeed, these drugs are infiltrated at the fat donor site for local anesthesia and for reduction of bleeding. This study analyzed the effects of these drugs on the viability of adipose-derived stem cells and on their inflammatory status. METHODS: Adipose-derived stem cells from lipoaspirates were grown in culture before being treated with different clinical doses of lidocaine at different times of exposure (1-24 h), and with adrenaline (1 µg/mL). Cytotoxicity was measured by lactate dehydrogenase assay and by flow cytometry with annexin V/propidium iodide staining. In parallel, the secretion of the proinflammatory cytokines tumor necrosis factor-alpha (TNFα), interleukin-6 (IL-6), and monocyte chemotactic protein-1 (MCP-1) was tested by enzyme-linked immunoassay. RESULTS: Lidocaine affected cell viability after 24 h, even when the cells were exposed for only 1 or 2 h. Apoptosis was not involved in lidocaine cytotoxicity. Regarding inflammation, no TNFα was produced, and lidocaine decreased the levels of IL-6 and MCP-1 in a dose-dependent manner. In contrast, adrenaline did not influence cell viability or cytokine secretions. CONCLUSIONS: Adipose tissue should be handled appropriately to remove lidocaine and adrenaline, with such procedures as washing and centrifugation. This study provides new insights into the use of lidocaine and adrenaline for fat transfer or stem cell isolation from lipoaspirates. LEVEL OF EVIDENCE II: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

High Content Imaging and Quantification of Microglia Phagocytosis In Vitro.

Microglia function as the tissue-specific resident macrophages of the nervous system, performing immune and non-immune functions. These functions are critical to development and to maintain homeostasis in the nervous system throughout the lifespan, and during brain injury or disease. One method by which microglia maintain homeostasis is phagocytosis of aberrant proteins, extracellular debris, synapses, or apoptotic cells. Phagocytic function can be changed by environmental or genetic risk factors that affect microglia. These protocols present a rapid and simple in vitro high-content imaging protocol for studying phagocytosis in the murine microglia BV-2 cell line. High-content imaging and analysis enable versatility of the assay, which can be used to test multiple experimental conditions, or as a screening tool. © 2023 Wiley Periodicals LLC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA. Basic Protocol 1: Phagocytosis of fluorescently labeled particles Basic Protocol 2: Examining modifications to phagocytosis by test substances Basic Protocol 3: High content imaging and analysis of phagocytic cells.

Curcumin-Encapsulated Nanomicelles Promote Tissue Regeneration in Zebrafish Eleutheroembryo.

Regenerative medicine is an emerging field of research aiming to understand the wound healing mechanisms and to develop new therapeutic strategies. Nanocarriers are used to improve drug bioavailability, solubility, and therapeutic abilities. In this study, we used for the first time curcumin loaded oligo kappa-carrageenan-graft-polycaprolactone (oligoKC-g-PCL) nanomicelles to investigate their regenerative potential using a model of tail amputation in zebrafish eleutheroembryo. First, we showed that curcumin encapsulated oligoKC-g-PCL spherical micelles had a mean size of 92 ± 32 nm and that micelles were successfully loaded with curcumin. These micelles showed a slow and controlled drug release over 72 h. The toxicity of curcumin nanomicelles was then tested on zebrafish eleutheroembryo based on the survival rate after 24 h. At nontoxic concentration, curcumin nanomicelles improved tail regeneration within 3 days postamputation, compared with empty micelles or curcumin alone. Furthermore, we demonstrated that curcumin nanomicelles increased the recruitment of neutrophils and macrophages 6 h postlesion. Finally, our study highlights the efficiency of oligoKC-g-PCL nanomicelles for encapsulation of hydrophobic molecules such as curcumin. Indeed, our study demonstrates that curcumin nanomicelles can modulate inflammatory reactions in vivo and promote regenerative processes. However, further investigations will be required to better understand the mechanisms sustaining regeneration and to develop new therapeutics.

Distribution of microglia/immune cells in the brain of adult zebrafish in homeostatic and regenerative conditions: Focus on oxidative stress during brain repair.

Microglia are macrophage-like cells exerting determinant roles in neuroinflammatory and oxidative stress processes during brain regeneration. We used zebrafish as a model of brain plasticity and repair. First, by performing L-plastin (Lcp1) immunohistochemistry and using transgenic Tg(mpeg1.1:GFP) or Tg(mpeg1.1:mCherry) fish, we analyzed the distribution of microglia/immune cells in the whole brain. Specific regional differences were evidenced in terms of microglia/immune cell density and morphology (elongated, branched, highly branched, and amoeboid). Taking advantage of Tg(fli:GFP) and Tg(GFAP::GFP) enabling the detection of endothelial cells and neural stem cells (NSCs), we highlighted the association of elongated microglia/immune cells with blood vessels and rounded/amoeboid microglia with NSCs. Second, after telencephalic injury, we showed that L-plastin cells were still abundantly present at 5 days post-lesion (dpl) and were associated with regenerative neurogenesis. Finally, RNA-sequencing analysis from injured telencephalon (5 dpl) confirmed the upregulation of microglia/immune cell markers and highlighted a significant increase of genes involved in oxidative stress (nox2, nrf2a, and gsr). The analysis of antioxidant activities at 5 dpl also revealed an upregulation of superoxide dismutase and persistent H2 O2 generation in the injured telencephalon. Also, microglia/immune cells were shown to be a source of oxidative stress at 5 dpl. Overall, our data provide a better characterization of microglia/immune cell distribution in the healthy zebrafish brain, highlighting some evolutionarily conserved features with mammals. They also emphasize that 5 days after injury, microglia/immune cells are still activated and are associated to a persistent redox imbalance. Together, these data raise the question of the role of oxidative stress in regenerative neurogenesis in zebrafish.

The Antiviral Potential of AdipoRon, an Adiponectin Receptor Agonist, Reveals the Ability of Zika Virus to Deregulate Adiponectin Receptor Expression.

Zika virus (ZIKV) is a pathogenic member of the flavivirus family, with several unique characteristics. Unlike any other arbovirus, ZIKV can be transmitted sexually and maternally, and thus produce congenital syndromes (CZS) due to its neurotropism. This challenges the search for safe active molecules that can protect pregnant women and their fetuses. In this context, and in the absence of any existing treatment, it seemed worthwhile to test whether the known cytoprotective properties of adiponectin and its pharmacological analog, AdipoRon, could influence the outcome of ZIKV infection. We showed that both AdipoRon and adiponectin could significantly reduce the in vitro infection of A549 epithelial cells, a well-known cell model for flavivirus infection studies. This effect was particularly observed when a pre-treatment was carried out. Conversely, ZIKV revealed an ability to downregulate adiponectin receptor expression and thereby limit adiponectin signaling.

Distribution of Adiponectin Receptors in the Brain of Adult Mouse: Effect of a Single Dose of the Adiponectin Receptor Agonist, AdipoRON, on Ischemic Stroke.

Adiponectin exhibits pleiotropic effects, including anti-inflammatory, anti-apoptotic, anti-oxidant, and neuroprotective ones. Although some studies have documented brain expression in different rodent models of its receptors, AdipoR1 and AdipoR2, their global distribution remains incomplete. Here, we demonstrated that both AdipoR are widely distributed in the brains of adult mice. Furthermore, by double immunostaining studies, we showed that AdipoR1 and AdipoR2 are mainly expressed in neurons and blood vessels. Then, considering the wide distribution of both receptors and the neuroprotective effects of adiponectin, we tested the therapeutic effect of a single injection of the adiponectin receptor agonist, AdipoRON (5 mg.kg-1), 24 h after stroke in a model of middle cerebral artery occlusion technique (MCAO). Under our experimental conditions, we demonstrated that AdipoRON did not modulate the infarct volume, cell death, neuroinflammatory parameters including microglia activation and oxidative stress. This study suggests that a protocol based on multiple injections of AdipoRON at a higher dose after MCAO could be considered to promote the therapeutic properties of AdipoRON on the brain repair mechanism and recovery.

Exposure to an organometal compound stimulates adipokine and cytokine expression in white adipose tissue.

OBJECTIVE: White adipose tissue (WAT) is now considered a defined tissue capable of interactions with other organ systems. WAT role in elevating the level of systemic chronic inflammation suggests that alterations in this tissue as the result of disease or environmental factors may influence the development and progression of various obesity-related pathologies. This study investigated WAT cell-specific responses to an organometal compound, trimethyltin (TMT), to determine possible contribution to induced inflammation. METHODS: Human primary mature adipocytes and macrophage differentiated THP-1 cells were cultured in TMT presence and relative toxicities and different adipokine levels were determined. The inflammatory response was examined in TMT presence for primary cells from obese ob/ob mice WAT, and after TMT injection in ob/ob mice. RESULTS: Both adipocytes and macrophages were resistant to cell death induced by TMT. However, adipocytes cultured in TMT presence showed increased expression of TNFα and IL-6, and modified leptin levels. In macrophage cultures, TMT also increased TNFα and IL-6, while MCP-1 and MIP-1α were decreased. In vivo, a single injection of TMT in ob/ob mice, elevated TNFα, MIP-1α and adiponectin in WAT. CONCLUSIONS: Elevation of the inflammatory related products can be induced by chemical exposure in adipocytes and macrophages, as well as murine WAT. These data suggest that numerous factors, including a systemic chemical exposure, can induce an inflammatory response from the WAT. Furthermore, when characterizing both chemical-induced toxicity and the progression of the chronic inflammation associated with elevated WAT content, such responses in this target tissue should be taken into consideration.

Deleterious Effects of Overfeeding on Brain Homeostasis and Plasticity in Adult Zebrafish.

Overweight and obesity are worldwide epidemic health threats. They recently emerged as disruptors of brain homeostasis leading to a wide variety of neurologic disorders. This study aims at developing a fast and easy overfeeding model using zebrafish for investigating the impact of overweight on brain homeostasis. We established a 4-week overfeeding protocol using commercially available dry food in an ad libitum-like feeding. In the diet-induced obesity/overweight (DIO) fish model, weight, size, and body mass index were increased compared with controls. Also, DIO fish displayed hyperglycemia, and had higher levels of advanced glycation end products and oxidative stress (4-hydroxynonenal [4-HNE]) in a peripheral organ (tail). Although overfed fish did not display major blood-brain barrier leakage, they showed an increased cerebral oxidative stress, blunted brain cell proliferation as well as a striking decreased locomotor activity. Interestingly, switching from an overfeeding to a normal diet partially improved peripheral and central disruptions induced by overfeeding in solely 2 weeks. As a conclusion, this study provides a rapid and easy overfeeding model in zebrafish with relevant peripheral and central disruptions. This model could open the way for further investigations to better understand by which mechanisms overfeeding could disturb brain homeostasis. It also reinforces and contrasts with another zebrafish overweight model, showing that the type of the food provided could impair differently brain homeostasis.

Impaired brain homeostasis and neurogenesis in diet-induced overweight zebrafish: a preventive role from A. borbonica extract.

Overweight and obesity are worldwide health concerns leading to many physiological disorders. Recent data highlighted their deleterious effects on brain homeostasis and plasticity, but the mechanisms underlying such disruptions are still not well understood. In this study, we developed and characterized a fast and reliable diet-induced overweight (DIO) model in zebrafish, for (1) studying the effects of overfeeding on brain homeostasis and for (2) testing different preventive and/or therapeutic strategies. By overfeeding zebrafish for 4 weeks, we report the disruption of many metabolic parameters reproducing human overweight features including increased body weight, body mass index, fasting blood glucose levels and liver steatosis. Furthermore, DIO fish displayed blood-brain barrier leakage, cerebral oxidative stress, neuroinflammation and decreased neurogenesis. Finally, we investigated the preventive beneficial effects of A. borbonica, an endogenous plant from Reunion Island. Overnight treatment with A. borbonica aqueous extract during the 4 weeks of overfeeding limited some detrimental central effects of DIO. In conclusion, we established a relevant DIO model in zebrafish demonstrating that overfeeding impairs peripheral and central homeostasis. This work also highlights the preventive protective effects of A. borbonica aqueous extracts in DIO, and opens a way to easily screen drugs aiming at limiting overweight and associated neurological disorders.

Expression of adiponectin receptors in the brain of adult zebrafish and mouse: Links with neurogenic niches and brain repair.

Adiponectin and its receptors (adipor) have been initially characterized for their role in lipid and glucose metabolism. More recently, adiponectin signaling was shown to display anti-inflammatory effects and to participate in brain homeostasis and neuroprotection. In this study, we investigated adipor gene expression and its regulation under inflammatory conditions in two complementary models: mouse and zebrafish. We demonstrate that adipor1a, adipor1b, and adipor2 are widely distributed throughout the brain of adult fish, in neurons and also in radial glia, behaving as neural stem cells. We also show that telencephalic injury results in a decrease in adipor gene expression, inhibited by an anti-inflammatory treatment (Dexamethasone). Interestingly, adiponectin injection after brain injury led to a consistent decrease (a) in the recruitment of microglial cells at the lesioned site and (b) in the proliferation of neural progenitors, arguing for a neuroprotective role of adiponectin. In a comparative approach, we investigate Adipor1 and Adipor2 gene distribution in the brain of mice and demonstrated their expression in regions shared with fish including neurogenic regions. We also document Adipor gene expression in mice after middle cerebral artery occlusion and lipopolysaccharide injection. In contrast to zebrafish, these inflammatory stimuli do no impact cerebral adiponectin receptor gene expression in mouse. This work provides new insights regarding adipor expression in the brain of fish, and demonstrates evolutionary conserved distribution of adipor with mouse. This is the first report of adipor expression in adult neural stem cells of fish, suggesting a potential role of adiponectin signaling during vertebrate neurogenesis. It also suggests a potential contribution of inflammation in the regulation of adipor in fish.

Enhanced effects of curcumin encapsulated in polycaprolactone-grafted oligocarrageenan nanomicelles, a novel nanoparticle drug delivery system.

One of the most effective strategies to enhance the bioavailability and the therapeutic effect of hydrophobic drugs is the use of nanocarriers. We have used κ-carrageenan extracted from Kappaphycus alvarezii to produce oligocarrageenan via an enzymatic degradation process. Polycaprolactone (PCL) chains were grafted onto the oligocarrageenans using a protection/deprotection technique yielding polycaprolactone-grafted oligocarrageenan. The resulting amphiphilic copolymers formed spherical nanomicelles with a mean size of 187 ± 21 nm. Hydrophobic drugs such as curcumin were efficiently encapsulated in the micelles and released within 24-72 h in solution. The micelles were non-cytotoxic and facilitated the uptake of curcumin by endothelial EA-hy926 cells. They also increased the anti-inflammatory effect of curcumin in TNF-alpha-induced inflammation experiments. Finally, in vivo experiments supported a lack of toxicity in zebrafish and thus the potential use of polycaprolactone-grafted oligocarrageenan to improve the delivery of hydrophobic compounds to different organs, including liver, lung and brain as shown in mice.

Tumor necrosis factor p55 and p75 receptors are involved in chemical-induced apoptosis of dentate granule neurons.

Localized tumor necrosis factor-alpha (TNFalpha) elevation has diverse effects in brain injury often attributed to signaling via TNFp55 or TNFp75 receptors. Both dentate granule cells and CA pyramidal cells express TNF receptors (TNFR) at low levels in a punctate pattern. Using a model to induce selective death of dentate granule cells (trimethyltin; 2 mg/kg, i.p.), neuronal apoptosis [terminal deoxynucleotidyl transferase-mediated dUTP-biotin in situ end labeling, active caspase 3 (AC3)] was accompanied by amoeboid microglia and elevated TNFalpha mRNA levels. TNFp55R (55 kDa type-1 TNFR) and TNFp75R (75 kDa type-2 TNFR) immunoreactivity in AC3(+) neurons displayed a pattern suggestive of receptor internalization and a temporal sequence of expression of TNFp55R followed by TNFp75R associated with the progression of apoptosis. A distinct ramified microglia response occurred around CA1 neurons and healthy dentate neurons that displayed an increase in the normal punctate pattern of TNFRs. Neuronal damage was decreased with i.c.v. injection of TNFalpha antibody and in TNFp55R-/-p75R-/- mice that showed higher constitutive mRNA levels for interleukin (IL-1alpha), macrophage inflammatory protein 1-alpha (MIP-1alpha), TNFalpha, transforming growth factor beta1, Fas, and TNFRSF6-assoicated via death domain (FADD). TNFp75R-/- mice showed exacerbated injury and elevated mRNA levels for IL-1alpha, MIP-1alpha, and TNFalpha. In TNFp55R-/- mice, constitutive mRNA levels for TNFalpha, IL-6, caspase 8, FADD, and Fas-associated phosphatase were higher; IL-1alpha, MIP-1alpha, and transforming growth factor beta1 lower. The mice displayed exacerbated neuronal death, delayed microglia response, increased FADD and TNFp75R mRNA levels, and co-expression of TNFp75R in AC3(+) neurons. The data demonstrate TNFR-mediated apoptotic death of dentate granule neurons utilizing both TNFRs and suggest a TNFp75R-mediated apoptosis in the absence of normal TNFp55R activity.

The type 1 interleukin 1 receptor is not required for the death of murine hippocampal dentate granule cells and microglia activation.

Alterations in inflammatory process, neuronal death, and glia response have been observed under manipulation of interleukin-1 (IL-1) and subsequent signaling through the type 1 IL-1 receptor (IL-1R1). To investigate the influence of IL-1R1 activation in the pathophysiology of a chemical-induced injury to the murine hippocampus, we examined the level and pattern of neuronal death and neuroinflammation in male weanling mice exposed to trimethyltin hydroxide (2.0 mg TMT/kg, i.p.). Dentate granule cell death occurred at 6 h post-TMT as detected by active caspase 3 immunostaining and presence of lectin positive microglia. The severity of neuronal death and microglia response increased by 12-24 h with elevations in mRNA levels for TNFalpha and IL-1alpha. In IL-1R1 null (IL-1R1-/-) mice, the pattern and severity of neuronal death at 24 or 72 h post-TMT was similar as compared to wildtype (WT) mice. In both groups, mRNA levels for TNFalpha and MIP-1alpha were elevated, no significant change was seen in either IL-1alpha or IL-1beta, and the early activation of microglia, including their ability to progress to a phagocytic phenotype, was maintained. Compared to WT mice, IL-1R1-/- mice displayed a limited glial fibrillary acidic protein (GFAP) astrocytic response, as well as a preferential induction in mRNA levels of Fas signaling components. Cumulatively, these results indicate that IL-1R1 activation is not necessary for TMT-induced death of dentate granule neurons or local activation of microglia; however, IL-1R1 signaling is involved in mediating the structural response of astrocytes to injury and may regulate apoptotic mechanisms via Fas signaling components.

Steroid Transport, Local Synthesis, and Signaling within the Brain: Roles in Neurogenesis, Neuroprotection, and Sexual Behaviors.

Sex steroid hormones are synthesized from cholesterol and exert pleiotropic effects notably in the central nervous system. Pioneering studies from Baulieu and colleagues have suggested that steroids are also locally-synthesized in the brain. Such steroids, called neurosteroids, can rapidly modulate neuronal excitability and functions, brain plasticity, and behavior. Accumulating data obtained on a wide variety of species demonstrate that neurosteroidogenesis is an evolutionary conserved feature across fish, birds, and mammals. In this review, we will first document neurosteroidogenesis and steroid signaling for estrogens, progestagens, and androgens in the brain of teleost fish, birds, and mammals. We will next consider the effects of sex steroids in homeostatic and regenerative neurogenesis, in neuroprotection, and in sexual behaviors. In a last part, we will discuss the transport of steroids and lipoproteins from the periphery within the brain (and vice-versa) and document their effects on the blood-brain barrier (BBB) permeability and on neuroprotection. We will emphasize the potential interaction between lipoproteins and sex steroids, addressing the beneficial effects of steroids and lipoproteins, particularly HDL-cholesterol, against the breakdown of the BBB reported to occur during brain ischemic stroke. We will consequently highlight the potential anti-inflammatory, anti-oxidant, and neuroprotective properties of sex steroid and lipoproteins, these latest improving cholesterol and steroid ester transport within the brain after insults.

CDDO and ATRA Instigate Differentiation of IMR32 Human Neuroblastoma Cells.

Neuroblastoma is the most common solid extra cranial tumor in infants. Improving the clinical outcome of children with aggressive tumors undergoing one of the multiple treatment options has been a major concern. Differentiating neuroblastoma cells holds promise in inducing tumor growth arrest and treating minimal residual disease. In this study, we investigated the effect of partial PPARγ agonist 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO) on human neuroblastoma IMR32 cells. Our results demonstrate that treatment with low concentration of CDDO and particularly in combination with all trans retinoic acid (ATRA) induced neurite outgrowth, increased the percentage of more than two neurites bearing cells, and decreased viability in IMR32 cells. These morphological changes were associated with an increase in expression of bonafide differentiation markers like ß3-tubulin and Neuron Specific Enolase (NSE). The differentiation was accompanied by a decrease in the expression of MYCN whose amplification is known to contribute to the pathogenesis of neuroblastoma. MYCN is known to negatively regulate NMYC downstream-regulated gene 1 (NDRG1) in neuroblastomas. MYCN down-regulation induced by CDDO correlated with increased expression of NDRG1. CDDO decreased Anaplastic Lymphoma Kinase (ALK) mRNA expression without affecting its protein level, while ATRA significantly down-regulated ALK. Antagonism of PPARγ receptor by T0070907 meddled with differentiation inducing effects of CDDO as observed by stunted neurite growth, increased viability and decreased expression of differentiation markers. Our findings indicate that IMR32 differentiation induced by CDDO in combination with ATRA enhances, differentiation followed by cell death via cAMP-response-element binding protein (CREB) independent and PPARγ dependent signaling mechanisms.

Diabetes, adult neurogenesis and brain remodeling: New insights from rodent and zebrafish models.

The prevalence of diabetes rapidly increased during the last decades in association with important changes in lifestyle. Diabetes and hyperglycemia are well-known for inducing deleterious effects on physiologic processes, increasing for instance cardiovascular diseases, nephropathy, retinopathy and foot ulceration. Interestingly, diabetes also impairs brain morphology and functions such as (1) decreased neurogenesis (proliferation, differentiation and cell survival), (2) decreased brain volumes, (3) increased blood-brain barrier leakage, (4) increased cognitive impairments, as well as (5) increased stroke incidence and worse neurologic outcomes following stroke. Importantly, diabetes is positively associated with a higher risk to develop Alzheimer disease. In this context, we aim at reviewing the impact of diabetes on neural stem cell proliferation, newborn cell differentiation and survival in a homeostatic context or following stroke. We also report the effects of hyper- and hypoglycemia on the blood-brain barrier physiology through modifications of tight junctions and transporters. Finally, we discuss the implication of diabetes on cognition and behavior.

Impaired constitutive and regenerative neurogenesis in adult hyperglycemic zebrafish.

A growing body of evidence supports hyperglycemia as a putative contributor to several brain dysfunctions observed in diabetes patients, such as impaired memory capacity, neural plasticity, and neurogenic processes. Thanks to the persistence of radial glial cells acting as neural stem cells, the brain of the adult zebrafish constitutes a relevant model to investigate constitutive and injury-induced neurogenesis in adult vertebrates. However, there is limited understanding of the impact of hyperglycemia on brain dysfunction in the zebrafish model. This work aimed at exploring the impact of acute and chronic hyperglycemia on brain homeostasis and neurogenesis. Acute hyperglycemia was shown to promote gene expression of proinflammatory cytokines (il1ß, il6, il8, and tnfα) in the brain and chronic hyperglycemia to impair expression of genes involved in the establishment of the blood-brain barrier (claudin 5a, zona occludens 1a and b). Chronic hyperglycemia also decreased brain cell proliferation in most neurogenic niches throughout the forebrain and the midbrain. By using a stab wound telencephalic injury model, the impact of hyperglycemia on brain repair mechanisms was investigated. Whereas the initial step of parenchymal cell proliferation was not affected by acute hyperglycemia, later proliferation of neural progenitors was significantly decreased by chronic hyperglycemia in the injured brain of fish. Taken together, these data offer new evidence highlighting the evolutionary conserved adverse effects of hyperglycemia on neurogenesis and brain healing in zebrafish. In addition, our study reinforces the utility of zebrafish as a robust model for studying the effects of metabolic disorders on the central nervous system. J. Comp. Neurol. 525:442-458, 2017. © 2016 Wiley Periodicals, Inc.

Acute and Chronic Models of Hyperglycemia in Zebrafish: A Method to Assess the Impact of Hyperglycemia on Neurogenesis and the Biodistribution of Radiolabeled Molecules.

Hyperglycemia is a major health issue that leads to cardiovascular and cerebral dysfunction. For instance, it is associated with increased neurological problems after stroke and is shown to impair neurogenic processes. Interestingly, the adult zebrafish has recently emerged as a relevant and useful model to mimic hyperglycemia/diabetes and to investigate constitutive and regenerative neurogenesis. This work provides methods to develop zebrafish models of hyperglycemia to explore the impact of hyperglycemia on brain cell proliferation under homeostatic and brain repair conditions. Acute hyperglycemia is established using the intraperitoneal injection of D-glucose (2.5 g/kg bodyweight) into adult zebrafish. Chronic hyperglycemia is induced by immersing adult zebrafish in D-glucose (111 mM) containing water for 14 days. Blood-glucose-level measurements are described for these different approaches. Methods to investigate the impact of hyperglycemia on constitutive and regenerative neurogenesis, by describing the mechanical injury of the telencephalon, dissecting the brain, paraffin embedding and sectioning with a microtome, and performing immunohistochemistry procedures, are demonstrated. Finally, the method of using zebrafish as a relevant model for studying the biodistribution of radiolabeled molecules (here,[18F]-FDG) using PET/CT is also described.