Markers Of Synaptogenesis Research Articles

Antidepressant-like effects of the Punica granatum and citalopram combination are associated with structural changes in dendritic spines of granule cells in the dentate gyrus of rats.

Introduction: Natural products such as phytoestrogens-enriched foods or supplements have been considered as an alternative therapy to reduce depressive symptoms associated with menopause. It is known that the aqueous extract of Punica granatum (AE-PG) exerts antidepressant-like effects by activating β-estrogen receptors and facilitates the antidepressant response of the clinical drug citalopram (CIT). However, the effects on neuroplasticity are unknown. Objectvie investigated the antidepressant-like response of combining AE-PG and CIT at sub-optimal doses, analyzing their effects on the formation and maturation of dendrite spines in granule cells as well as on the dendrite complexity. Methods: Ovariectomized Wistar rats (3-month-old) were randomly assigned to one of the following groups: A) control (saline solution as vehicle of CIT and AE-PG, B) AE-PG at a sub-threshold dose (vehicle of CIT plus AE-PG at 0.125mg/kg), C) CIT at a sub-threshold dose (0.77mg/kg plus vehicle of AE-PG), and D) a combination of CIT plus AE-PG (0.125mg/kg and 0.77mg/kg, respectively). All rats were treated intraperitoneally for 14 days. Antidepressant-like effects were evaluated using the force swimming test test (FST). The complexity of dendrites and the number and morphology of dendrite spines of neurons were assessed in the dentate gyrus after Golgi-Cox impregnation. The expressions of the mature brain-derived neurotrophic factor (mBDNF) in plasma and of mBDNF and synaptophysin in the hippocampus, as markers of synaptogenesis, were also determined. Results: Administration of CIT combined with AE-PG, but not alone, induced a significant antidepressant-like effect in the FST with an increase in the dendritic complexity and the number of dendritic spines in the dentate gyrus (DG) of the hippocampus, revealed by the thin and stubby categories of neurons at the granular cell layer. At the same time, an increase of mBDNF and synaptophysin expression was observed in the hippocampus of rats that received the combination of AE-PG and CIT.

Delayed Chronic Acidic Postconditioning Improves Poststroke Motor Functional Recovery and Brain Tissue Repair by Activating Proton-Sensing TDAG8.

Acidic postconditioning by transient CO2 inhalation applied within minutes after reperfusion has neuroprotective effects in the acute phase of stroke. However, the effects of delayed chronic acidic postconditioning (DCAPC) initiated during the subacute phase of stroke or other acute brain injuries are unknown. Mice received daily DCAPC by inhaling 5%/10%/20% CO2 for various durations (three cycles of 10- or 20-min CO2 inhalation/10-min break) at days 3-7, 7-21, or 3-21 after photothrombotic stroke. Grid-walk, cylinder, and gait tests were used to assess motor function. DCAPC with all CO2 concentrations significantly promoted motor functional recovery, even when DCAPC was delayed for 3-7 days. DCAPC enhanced the puncta density of GAP-43 (a marker of axon growth and regeneration) and synaptophysin (a marker of synaptogenesis) and reduced the amoeboid microglia number, glial scar thickness and mRNA expression of CD16 and CD32 (markers of proinflammatory M1 microglia) compared with those of the stroke group. Cerebral blood flow (CBF) increased in response to DCAPC. Furthermore, the mRNA expression of TDAG8 (a proton-activated G-protein-coupled receptor) was increased during the subacute phase of stroke, while DCAPC effects were blocked by systemic knockout of TDAG8, except for those on CBF. DCAPC reproduced the benefits by re-expressing TDAG8 in the peri-infarct cortex of TDAG8-/- mice infected with HBAAV2/9-CMV-TDAG8-3flag-ZsGreen. Taken together, we first showed that DCAPC promoted functional recovery and brain tissue repair after stroke with a wide therapeutic time window of at least 7 days after stroke. Brain-derived TDAG8 is a direct target of DCAPC that induces neuroreparative effects.

Molecular Markers in Maternal Blood Exosomes Allow Early Detection of Fetal Alcohol Spectrum Disorders.

Prenatal alcohol exposure can cause developmental abnormalities (fetal alcohol spectrum disorders; FASD), including small eyes, face and brain, and neurobehavioral deficits. These cannot be detected early in pregnancy with available imaging techniques. Early diagnosis could facilitate development of therapeutic interventions. Banked human fetal brains and eyes at 9-22 weeks' gestation were paired with maternal blood samples, analyzed for morphometry, protein, and RNA expression, and apoptotic signaling. Alcohol (EtOH)-exposed (maternal self-report) fetuses were compared with unexposed controls matched for fetal age, sex, and maternal race. Fetal brain-derived exosomes (FB-E) were isolated from maternal blood and analyzed for protein, RNA, and apoptotic markers. EtOH use by mothers, assessed by self-report, was associated with reduced fetal eye diameter, brain size, and markers of synaptogenesis. Brain caspase-3 activity was increased. The reduction in eye and brain sizes were highly correlated with amount of EtOH intake and caspase-3 activity. Levels of several biomarkers in FB-E, most strikingly myelin basic protein (MBP; r > 0.9), correlated highly with morphological abnormalities. Reduction in FB-E MBP levels was highly correlated with EtOH exposure (p < 1.0 × 10-10). Although the morphological features of FAS appear long before they can be detected by live imaging, FB-E in the mother's blood may contain markers, particularly MBP, that predict FASD.

Resveratrol-mediated neurorestoration after cerebral ischemic injury - Sonic Hedgehog signaling pathway

AimsResveratrol pretreatment can decrease ischemic cerebral injury and enhance proliferation of neural stem cells via mediation of Sonic Hedgehog signaling. However, it is relatively little known about whether neurorestorative effects of resveratrol are mediated by Shh signaling in ischemic cerebral injury. The present study tests whether the Shh signaling pathway mediates resveratrol to promote neurorestoration of ischemic cerebral injury. Materials and methodsRats or neurons before middle cerebral artery occlusion/reperfusion (MCAO/R) or oxygen-glucose deprivation/reoxygenation (OGD/R) injury were pretreated with resveratrol. Immunohistochemistry is used to be determined BrdU+/DCX+, BrdU+/Nestin+ and BrdU+/NG2+ cell (markers of new proliferated neural stem/progenitor and oligodendrocyte precursor cell, respectively), BrdU+/MAP2+ and BrdU+/CNPase+ cell (markers of new mature neuron and oligodendrocyte, respectively), BrdU+/TUNEL+ cell (marker of apoptosis for new proliferated cell), SY, NF200, Iba-1 and GFAP (markers of synaptogenesis, axon, microglia and astrocyte, respectively). Shh and Gli-1 mRNAs were detected by RT-PCR assay. Iba-1, GFAP, Shh and Gli-1 proteins were detected by Western blot. Key findingsResveratrol pretreatment significantly reduced neurological deficit scores, promoted proliferation, differentiation, migration and survival of neural stem/progenitor and oligodendrocyte precursor cells, inhibited astrocyte and microglia activation, strengthened synaptophysin and NF200 expression, at the same time, promoted neurite outgrowth of neurons. Meanwhile, expression levels of Shh and Gli-1 proteins were significantly increased and Gli-1 translocated into the nucleus. However, cyclopamine, a Smo inhibitor, canceled the above effects of resveratrol. ConclusionsIt may be mediated, at least partly, by the Shh signaling pathway that resveratrol pretreament promote neurorestoration of ischemic cerebral injury.

The effect of exercise on memory and BDNF signaling is dependent on intensity.

The aims of the present study were to investigate in brain of adult rats (1) whether exercise-induced activation of brain-derived neurotrophic factor (BDNF)/tropomyosin-related kinase B (TrkB) pathway is dependent on exercise intensity modality and (2) whether exercise-induced improvement of memory is proportional to this pathway activation. Wistar rats were subjected to low (12m/min) or high (18m/min) exercise intensity on horizontal treadmill (30min/day, 7 consecutive days) that corresponds to ~ 40 and 70% of maximal aerobic speed, respectively. Animals treated with scopolamine to induce memory impairment were subjected to novel object recognition test to assess potential improvement in cognitive function. Expressions of BDNF, phosphorylated TrkB receptors, synaptophysin (a marker of synaptogenesis), c-fos (a neuronal activity marker) and phosphorylated endothelial nitric oxide synthase (a cerebral blood flow marker) were measured in prefrontal cortex and hippocampus of different groups of rats. In terms of cognition, our data reported that only the most intense exercise improves memory performance. Our data also revealed that BDNF pathway is dependent on intensity modality of exercise with a gradual effect in hippocampus whereas only the highest intensity leads to this pathway activation in prefrontal cortex. Our study revealed that memory improvement through BDNF pathway activation is dependent on exercise intensity. While reporting that our protocol is sufficient to improve cognition in animals with impaired memory, our data suggest that prefrontal cortex is possibly a more suitable structure than hippocampus when neuroplastic markers are used to mirror potential improvement in memory performance.

Nutritional Intervention for Developmental Brain Damage: Effects of Lactoferrin Supplementation in Hypocaloric Induced Intrauterine Growth Restriction Rat Pups.

Introduction: Intrauterine Growth Restriction (IUGR) refers to an impaired development of the fetus and hence results in adverse neurodevelopmental and psychiatric consequences later in life. Lactoferrin (Lf) is a glycoprotein present in milk that has already shown neuroprotective effects through its anti-inflammatory and antioxidant properties on impaired developing brains. The aim of this study was to characterize a rat model of IUGR and assess the neuroprotective effect of a nutritional supplementation with bovine Lf during pregnancy and lactation on this model.Methods: A model of 50% gestational caloric restriction (CR) was used. Three groups were designed, and pregnant rats had either ad libitum access to food (control group, CTL) or 50% of the controls' intake (restricted group, IUGR). The diet was isocaloric and supplemented with bovine Lf for the caloric restricted dams (restricted-Lf, IUGR_Lf). At postnatal day 7 and 21, advanced ex-vivo diffusion MRI techniques at 9.4T were used to investigate brain cortical and white matter microstructure. Further, genes and proteins involved in structure (synaptophysin, MBP), microglia (Iba-1), metabolism (MCT2, βCaMKII) and apoptosis (Bcl-2) were analyzed in the cortex and striatum. In the cortex, the number of parvalbumin immunoreactive interneurons and their perineuronal nets were quantified. Behavioral tests were performed at P31.Results: Effects of the CR were significant in the cortex and striatum with reduction of synaptophysin (marker of synaptogenesis) at P7 and MBP (marker of myelin) at P21 in the cortex. Indeed, MCT2 (energy metabolism), Bcl-2 (anti-apoptotic protein) and βCaMKII (synapse activity) expressions were reduced in IUGR groups at P7. In the striatum NG2 (marker of oligodendrocyte precursor cells) and Bcl-2 at P7 as well as βCaMKII at P21 were decreased following IUGR and restored by Lf. Cortical microstructure was impaired following CR with partial effect of Lf. Lf prevented oxidative stress induced parvalbumin interneurons impairments whereas striatum and external capsule showed alterations in microstructure depicted by diffusion MRI, which were also partially reversed by Lf.Discussion and Conclusion: The model of 50% caloric restriction induced mild impairment partially reversed by nutritional intervention using Lf during pregnancy and lactation.

Brain-derived Neurotrophic Factor Pathway after Downhill and Uphill Training in Rats

The elevation of brain-derived neurotrophic factor (BDNF) levels in the brain and the subsequent phosphorylation of its cognate tropomyosin-related kinase B (TrkB) receptors at tyrosine 816 (pTrkB) are largely involved in the positive effect of aerobic exercise on brain functioning. Although BDNF levels were reported to increase in proportion with exercise intensity, the effect of the type of contraction is unknown. Therefore, the cerebral BDNF/TrkB pathway was investigated after uphill and downhill treadmill activities at equivalent intensity to preferentially induce eccentric and concentric contractions, respectively. A treadmill activity (30 min·d for seven consecutive days) either in a horizontal position at two different speeds to modulate intensity (experiment 1) or at three different inclinations (null, -10%, and +5%) but at equivalent intensity to modulate the type of contraction (experiment 2) was induced in rats. Both experiments included sedentary rats. Levels of BDNF, pTrkB, synaptophysin (marker of synaptogenesis), endothelial nitric oxide synthase phosphorylated at serine 1177 (peNOS), and c-fos levels (indicators of elevation in blood flow in the cerebrovasculature and neuronal activity, respectively) were measured in motor- and cognition-related brain regions using Western blotting analysis. Experiment 1 indicated that treadmill activity induces an intensity-dependent increase in peNOS, c-fos, and BDNF levels. Experiment 2 showed that intensity of exercise as well as activation of the cerebral BDNF pathway, and synaptogenesis did not differ among horizontal, uphill, and downhill treadmill activities. The cerebral response of the BDNF pathway to a treadmill activity is dependent on exercise intensity, but not on the type of contraction (eccentric vs concentric).

Let-7i inhibition enhances progesterone-induced functional recovery in a mouse model of ischemia

Progesterone (P4) is a potent neuroprotectant and a promising therapeutic for stroke treatment. However, the underlying mechanism(s) remain unclear. Our laboratory recently reported that brain-derived neurotrophic factor (BDNF) is a critical mediator of P4's protective actions and that P4-induced BDNF release from cortical astrocytes is mediated by a membrane-associated progesterone receptor, Pgrmc1. Here, we report that the microRNA (miRNA) let-7i is a negative regulator of Pgrmc1 and BDNF in glia and that let-7i disrupts P4-induced BDNF release and P4's beneficial effects on cell viability and markers of synaptogenesis. Using an in vivo model of ischemia, we demonstrate that inhibiting let-7i enhances P4-induced neuroprotection and facilitates functional recovery following stroke. The discovery of such factors that regulate the cytoprotective effects of P4 may lead to the development of biomarkers to differentiate/predict those likely to respond favorably to P4 versus those that do not.

Dipeptide Mimetic of the BDNF GSB-106 with Antidepressant-Like Activity Stimulates Synaptogenesis.

Dipeptide mimetic of the brain-derived neurotrophic factor bis(N-monosuccinyl-L-seryl-L-lysine) hexamethylenediamide (working name GSB-106), which reproduces the homodimeric structure of BDNF and the beta-turn of its fourth loop, activates TrkB, AKT, and ERK, exhibits neuroprotective and antidepressant activity, and is able to stimulate neurogenesis in the hippocamp of stressed mice. Using Western blot hybridization and synaptophysin (synaptogenesis marker), we showed the ability of chronically administered GSB-106 to stimulate synaptogenesis, increasing the synaptic density in the hippocamp by 50%. Under the same conditions, GSB-106 exhibited antidepressant activity (decreased (by 18%) immobility of animals in Porsolt test), which may be associated with the stimulation of neurogenesis and synaptogenesis in the hippocamp.

Thrombospondin-1 Gene Deficiency Worsens the Neurological Outcomes of Traumatic Brain Injury in Mice.

Background: Thrombospondin-1 (TSP-1) is an extracellular matrix protein that plays multiple physiological and pathophysiological roles in the brain. Experimental reports suggest that TSP-1 may have an adverse role in neuronal function recovery under certain injury conditions. However, the roles of TSP-1 in traumatic brain injury (TBI) have not been elucidated. In this study we for the first time investigated the roles of TSP-1 in a controlled cortical impact (CCI) model of TBI in TSP-1 knockout (TSP-1 KO) and wild type (WT) mice.Methods: We examined blood brain-barrier (BBB) damage using at 1 day post-TBI by measuring Evans Blue leakage, and neurological functional recovery at 3 weeks post-TBI by measuring neurological severity score (NSS), wire gripping, corner test and Morris Water Maze (MWM). Mechanistically, we quantified pro-angiogenic biomarkers including cerebral vessel density, vascular endothelial growth factors (VEGF) and angiopoietin-1 (Ang-1) protein expression, synaptic biomarker synaptophysin, and synaptogenesis marker brain-derived neurotrophic factor (BDNF) protein expression in contralateral and ipsilateral (peri-lesion) cortex at 21 days after TBI using immunohistochemistry and Western Blot.Results: TSP-1 is upregulated at early phase of TBI in WT mice. Compared to WT mice, TSP-1 KO (1) significantly worsened TBI-induced BBB leakage at 1 day after TBI; (2) had similar lesion size as WT mice at 3 weeks after TBI; (3) exhibited a significantly worse neurological deficits in motor and cognitive functions; (4) had no significant difference in cerebral vessel density, but significant increase of VEGF and Ang-1 protein expressions in peri-lesion cortex; (5) significantly increased BDNF but not synaptophysin protein level in peri-lesion cortex compared to sham, but both synaptophysin and BDNF expressions were significantly decreased in contralateral cortex compared to WT.Conclusion: Our results suggest that TSP-1 may be beneficial for maintaining BBB integrity in the early phase and functional recovery in late phase after TBI. The molecular mechanisms of TSP-1 in early BBB pathophysiology, and long-term neurological function recovery after TBI need to be further investigated.

Altered expression and localization of synaptophysin in developing cerebellar cortex of neonatal rats due to maternal diabetes mellitus

There is sufficient evidence that diabetes during pregnancy is associated with a higher risk of neurodevelopmental anomalies including learning deficits, behavioral problems and motor dysfunctions in the offspring. Synaptophysin (SYP) is an integral membrane protein of synaptic vesicles and is considered as a marker for synaptogenesis and synaptic density. This study aimed to examine the effects of maternal diabetes in pregnancy on the expression and localization of SYP in the developing rat cerebellum. Wistar female rats were maintained diabetic from a week before pregnancy through parturition and male offspring was euthanized at postnatal day (P) 0, 7, and 14. The results revealed a significant down-regulation in the mRNA expression of SYP in the offspring born to diabetic animals at both P7 and P14 (P<0.05 each). One week after birth, there was a significant reduction in the localization of SYP expression in the external granular (EGL) and in the molecular (ML) layers of neonates born to diabetic animals (P<0.05 each). We also found a marked decrease in the expression of SYP in all of the cerebellar cortical layers of STZ-D group pups at P14 (P<0.05 each). Moreover, our results revealed no significant changes in either expression or localization of SYP in insulin-treated group pups when compared with the controls (P≥0.05 each). The present study demonstrated that maternal diabetes has adverse effects on the synaptogenesis in the offspring's cerebellum. Furthermore, the rigid maternal blood glucose control in the most cases normalized these negative impacts.

The Mini-Spadin, an efficient alternate to Spadin in the depression treatment

ObjectivesWe previously discovered spadin as a new antidepressant drug concept. Spadin exerts its antidepressant actions on the TREK-1 potassium channel, a new antidepressant (AD) target. We have shown that spadin acts more rapidly in comparison to other ADs. We have pointed out that spadin induced neurogenesis after only 4-day treatments. We have demonstrated that spadin did not display side effects at the cardiac level and on TREK-1 controlled functions such as stroke, epilepsy or pain.ObjectivesWith the final goal to make spadin a drug for human clinic, our objective was to find analogs of spadin demonstrating a better affinity or a better in vivo stability or both.MethodsSeveral analogs of spadin were synthesized. Their ability to block the TREK-1 channel activity were first tested by electrophysiology on HEK293 cells stably transfected with TREK-1 channels. AD effects were measured by using the forced swim test and the novelty suppressed feeding test. Neurogenesis was investigated by measuring the expression level of the synaptic protein PSD-95 in in vitro cultured neurons.ResultsOur data allow us to identify a shortened spadin, called mini-spadin, that displayed the same AD properties as spadin and a 400 fold increase in the TREK-1 affinity. Mini-spadin increased the synaptogenesis marker PSD95 levels after only 24 hours of treatment, suggesting that like spadin, mini-spadin was able to induce neurogenesis and synaptogenesis.ConclusionsEven if further experiments are required, the mini-spadin appears to be more efficient than spadin offering a very promising alternate to spadin as human drug.Disclosure of interestThe authors have not supplied their declaration of competing interest.

The impacts of diabetes in pregnancy on hippocampal synaptogenesis in rat neonates

Diabetes during the pregnancy period impairs hippocampal development, and is associated with neurocognitive and neurobehavioral problems in the offspring. Synaptogenesis is one of the most important events in the development of the nervous system, and is known as a mechanism by which the memory process takes place. Synaptophysin (SYP) is an integral membrane protein of synaptic vesicles in the hippocampus involved also in learning and memory. The present study aimed to examine the effects of maternal diabetes on the expression and distribution pattern of SYP, as a marker of synaptogenesis, in the developing rat hippocampus using Immunofluorescence staining and real-time PCR. Wistar female rats were maintained as diabetic from a week before pregnancy through parturition and male offspring was euthanized at postnatal day (P) 0, 7, and 14. Our results showed a significant down-regulation in mRNA expression of SYP in the offspring born to diabetic animals at P7, and P14 (P⩽0.05 each). Regarding to the density of SYP expressing hippocampal neurons, we found a marked decrease in the distribution pattern of SYP in all hippocampal subfields of Streptozotocin (STZ)-D group rat neonates, especially in one and two weeks of age (P⩽0.05 each). Moreover, the results revealed no significant changes in either gene expression or distribution pattern of SYP – positive neurons in insulin-treated group compared with the controls. The present study demonstrated that diabetes in pregnancy has negative impacts on synaptogenesis in the offspring’s hippocampus. Furthermore, the rigid maternal glycaemia control by insulin treatment in most cases normalized these effects.

In vitro and in vivo regulation of synaptogenesis by the novel antidepressant spadin.

We have described a novel antidepressant peptide, spadin, that acts by blocking the TWIK-related-potassium channel, type 1 (TREK-1). Here, we examined possible mechanisms of action of spadin at both molecular and cellular levels. Effects of spadin were measured in primary cultures of neurons or tissues from mice injected i.v. with spadin. Western blots, qPCR, histochemical and electrophysiological techniques were used. In vitro, spadin increased neuronal membrane potential and activated both the MAPK and PI3K signalling pathways, in a time- and concentration-dependent manner. The latter pathway was involved in the protective effect of spadin against staurosporine-induced apoptosis. Also, spadin enhanced both mRNA expression and protein of two markers of synaptogenesis, the post-synaptic density protein of 95 kDalton (PSD-95) and synapsin. We confirmed these effects on synaptogenesis by the observation that spadin treatment significantly increased the proportion of mature spines in cortical neurons. Finally, in vivo injections of spadin led to a rapid increase in both mRNA expression and protein level of brain-derived neurotrophic factor (BDNF) in the hippocampus, confirming the antidepressant action of the peptide. We argue for a new role of spadin in synaptogenesis as both PSD-95 and synapsin mRNA expression and protein levels were further enhanced in the hippocampus, following treatment in vivo with the peptide. These findings provide new mechanisms of action for the rapidly acting antidepressant peptide spadin by stimulating expression of BDNF and synaptic proteins, both in vitro and in vivo.

Low-level laser therapy for traumatic brain injury in mice increases brain derived neurotrophic factor (BDNF) and synaptogenesis.

Transcranial low-level laser (light) therapy (LLLT) is a new non-invasive approach to treating a range of brain disorders including traumatic brain injury (TBI). We (and others) have shown that applying near-infrared light to the head of animals that have suffered TBI produces improvement in neurological functioning, lessens the size of the brain lesion, reduces neuroinflammation, and stimulates the formation of new neurons. In the present study we used a controlled cortical impact TBI in mice and treated the mice either once (4 h post-TBI, 1-laser), or three daily applications (3-laser) with 810 nm CW laser 36 J/cm(2) at 50 mW/cm(2). Similar to previous studies, the neurological severity score improved in laser-treated mice compared to untreated TBI mice at day 14 and continued to further improve at days 21 and 28 with 3-laser being better than 1-laser. Mice were sacrificed at days 7 and 28 and brains removed for immunofluorescence analysis. Brain-derived neurotrophic factor (BDNF) was significantly upregulated by laser treatment in the dentate gyrus of the hippocampus (DG) and the subventricular zone (SVZ) but not in the perilesional cortex (lesion) at day 7 but not at day 28. Synapsin-1 (a marker for synaptogenesis, the formation of new connections between existing neurons) was significantly upregulated in lesion and SVZ but not DG, at 28 days but not 7 days. The data suggest that the benefit of LLLT to the brain is partly mediated by stimulation of BDNF production, which may in turn encourage synaptogenesis. Moreover the pleiotropic benefits of BDNF in the brain suggest LLLT may have wider applications to neurodegenerative and psychiatric disorders. Neurological Severity Score (NSS) for TBI mice.

Differential effects of prenatal chronic high-decibel noise and music exposure on the excitatory and inhibitory synaptic components of the auditory cortex analog in developing chicks (Gallus gallus domesticus)

Proper development of the auditory cortex depends on early acoustic experience that modulates the balance between excitatory and inhibitory (E/I) circuits. In the present social and occupational environment exposure to chronic loud sound in the form of occupational or recreational noise, is becoming inevitable. This could especially disrupt the functional auditory cortex development leading to altered processing of complex sound and hearing impairment. Here we report the effects of prenatal chronic loud sound (110-dB sound pressure level (SPL)) exposure (rhythmic [music] and arrhythmic [noise] forms) on the molecular components involved in regulation of the E/I balance in the developing auditory cortex analog/Field L (AuL) in domestic chicks. Noise exposure at 110-dB SPL significantly enhanced the E/I ratio (increased expression of AMPA receptor GluR2 subunit and glutamate with decreased expression of GABA(A) receptor gamma 2 subunit and GABA), whereas loud music exposure maintained the E/I ratio. Expressions of markers of synaptogenesis, synaptic stability and plasticity i.e., synaptophysin, PSD-95 and gephyrin were reduced with noise but increased with music exposure. Thus our results showed differential effects of prenatal chronic loud noise and music exposures on the E/I balance and synaptic function and stability in the developing auditory cortex. Loud music exposure showed an overall enrichment effect whereas loud noise-induced significant alterations in E/I balance could later impact the auditory function and associated cognitive behavior.

Pharmacological concentrations of irisin increase cell proliferation without influencing markers of neurite outgrowth and synaptogenesis in mouse H19-7 hippocampal cell lines

Aims/HypothesisIrisin is a novel, myocyte secreted, hormone that has been proposed to mediate the beneficial effects of exercise on metabolism. Irisin is expressed, at lower levels, in human brains and knock-down of the precursor of irisin, FNDC5, decreases neural differentiation of mouse embryonic stem cells. No previous studies have evaluated whether irisin may directly regulate hippocampal neurogenesis in mouse hippocampal neuronal (HN) cells. MethodsHippocampal neurogenesis and irisin signaling were studied in vitro using mouse H19-7 HN cell lines. ResultsWe observed that cell proliferation is regulated by irisin in a dose-dependent manner in mouse H19-7 HN cells. Specifically, physiological concentrations of irisin, 5 to 10nmol/L, had no effect on cell proliferation when compared to control. By contrast, pharmacological concentrations of irisin, 50 to 100nmol/L, increased cell proliferation when compared to control. Similar to these results regarding irisin's effects on cell proliferation, we also observed that only pharmacological concentrations of irisin increased STAT3, but not AMPK and/or ERK, activation. Finally, we observed that irisin did not activate either microtubule-associated protein 2, a specific neurite outgrowth marker, or Synapsin, a specific synaptogenesis marker in mouse H19-7 HN cells. Conclusions/InterpretationsOur data suggest that irisin, in pharmacological concentrations, increases cell proliferation in mouse H19-7 HN cells via STAT3, but not AMPK and/or ERK, signaling pathways. By contrast, neither physiological nor pharmacological concentrations of irisin alter markers of hippocampal neurogenesis in mouse H19-7 HN cell lines.

Amylin-induced downregulation of hippocampal neurogenesis is attenuated by leptin in a STAT3/AMPK/ERK-dependent manner in mice

Both leptin and insulin sensitivity have been linked with pathophysiological processes involving the central nervous system in general, and the hippocampus in particular, but the role of leptin in hippocampal neurogenesis has not yet been elucidated. Also, no previous studies have evaluated whether amylin or the endogenous insulin sensitiser adiponectin interact with leptin to alter hippocampal neurogenesis in mouse hippocampal neuronal (HN) cells or investigated the role of leptin, amylin or adiponectin signalling in mouse HN cells. Hippocampal neurogenesis and leptin, amylin and adiponectin signalling were studied in vitro using mouse H19-7 HN cell lines. Amylin decreased cell proliferation in a dose-dependent manner. This effect was diminished by leptin administration and was dependent on signal transducer and activator of transcription 3 (STAT3)/AMP-activated protein kinase (AMPK)/extracellular signal-regulated kinase (ERK). Adiponectin effects were null. We also observed, using immunocytochemical analysis, that amylin decreased activation of microtubule-associated protein 2, a specific neurite outgrowth marker, and synapsin, a specific synaptogenesis marker. By contrast, both effects were attenuated by co-administration of leptin. Finally, we observed that these effects were blocked by pre-treatment with AG490, a STAT3 inhibitor, and STAT3 small interfering RNA administration. Our data suggest that amylin in pharmacological concentrations may have a neurotoxic effect whereas leptin in physiological and pharmacological concentrations has a protective effect counteracting amylin-decreased hippocampal neurogenesis via STAT3/AMPK/ERK signalling in mouse H19-7 HN cell lines. Overall, our data support a novel role for leptin and amylin in the processes of mouse hippocampal neurogenesis and provide new insights into the mechanisms of neurogenic regulation.

Ipsilateral versus contralateral spontaneous post-stroke neuroplastic changes: Involvement of BDNF?

Stroke is a leading cause of death and disability in industrialized countries. Although surviving patients exhibit a certain degree of restoration of function attributable to brain plasticity, the majority of stroke survivors has to struggle with persisting deficits. In order to potentiate post-stroke recovery, several rehabilitation therapies have been undertaken and many experimental studies have reported that brain-derived neurotrophic factor (BDNF) is central to many facets of neuroplastic processes. However, although BDNF role in brain plasticity is well characterized through strategies that manipulate its content, the involvement of this neurotrophin in spontaneous post-stroke recovery remains to be clarified. Besides, while the neuroplastic role of BDNF is restricted to its mature form, most studies investigating the proper effect of ischemia on post-stroke BDNF metabolism focused on mRNA or total protein expressions. In addition, these studies are mainly performed in brain regions collected either at or around the lesion site. Therefore, the objective of the present study was to investigate in both hemispheres, the long-term expression (up to one month) of both pro- and mature BDNF forms in rats subjected to photothrombotic ischemia. These assessments were performed in the cortex and in the hippocampus, two regions known to subserve functional recovery after stroke and were coupled to the study of synaptophysin expression, a marker of synaptogenesis. Our study reports that stroke induces an early and transient increase (4h) in mature BDNF expression in the cortex of both hemispheres that was associated with a delayed rise (30d) in synaptophysin levels ipsilateraly. In both hippocampal territories, the pattern of mature BDNF expression shows a more delayed increase (from 8 to 30d), which coincides with the evolution of synaptophysin expression. Interestingly, in these hippocampal territories, pro-BDNF levels evolve differently suggesting a differential gene regulation between the two hemispheres. While highlighting the complexity of changes in BDNF metabolism after stroke, our data suggest that BDNF involvement in spontaneous post-stroke plasticity is region-dependent.

Gestational-neonatal iron deficiency suppresses and iron treatment reactivates IGF signaling in developing rat hippocampus

Gestational-neonatal iron deficiency, a common micronutrient deficiency affecting the offspring of more than 30% of pregnancies worldwide, leads to long-term cognitive and behavioral abnormalities. Preclinical models of gestational-neonatal iron deficiency result in reduced energy metabolism and expression of genes critical for neuronal plasticity and cognitive function, which are associated with a smaller hippocampal volume and abnormal neuronal dendrite growth. Because insulin-like growth factor (IGF) modulates early postnatal cellular growth, differentiation, and survival, we used a dietary-induced rat model to assess the effects of gestational iron deficiency on activity of the IGF system. We hypothesized that gestational iron deficiency attenuates postnatal hippocampal IGF signaling and results in downstream effects that contribute to hippocampal anatomic and functional deficits. At postnatal day (P) 15 untreated gestational-neonatal iron deficiency markedly suppressed hippocampal IGF activation and protein kinase B signaling, and reduced neurogenesis, while elevating extracellular signal-regulated kinase 1/2 signaling and hypoxia-inducible factor-1α expression. Iron treatment beginning at P7 restored IGF signaling, increased neurogenesis, and normalized all parameters by the end of rapid hippocampal differentiation (P30). Expression of the neuron-specific synaptogenesis marker, disc-large homolog 4 (PSD95), increased more rapidly than the glia-specific myelination marker, myelin basic protein, following iron treatment, suggesting a more robust response to iron therapy in IGF-I-dependent neurons than IGF-II-dependent glia. Collectively, our findings suggest that IGF dysfunction is in part responsible for hippocampal abnormalities in untreated iron deficiency. Early postnatal iron treatment of gestational iron deficiency reactivates the IGF system and promotes neurogenesis and differentiation in the hippocampus during a critical developmental period.