Granular Cell Layer Research Articles

Gas chromatography-mass spectrometry elucidation and antipsoriatic activity on developed herbal formulations from Carissa congesta, Catharanthus roseus, Annona squamosa, and Polyalthia longifolia Plant Extracts

Background: Annonaceae and Apocynaceae families are known for their plethora of pharmacotherapeutic potential. Objectives: To evaluate antipsoriatic potential (ultraviolet [UV]-induced photodermatitis and tail model) and gas chromatography-mass spectrometry (GC-MS) studies on developed formulations from the plant extracts. Materials and Methods: Formulations of ethanolic extracts of Carissa congesta and Catharanthus roseus and petroleum ether extracts of Annona squamosa and Polyalthia longifolia were evaluated for antipsoriatic activity (UV-induced photodermatitis and tail model) at 250 and 500 mg/kg. GC-MS studies were done subsequently after 6 months. Formulation batches were tested by different tests, viz., pH, viscosity, spreadability, washability, homogeneity, grittiness, drug content, Sudan red, bleeding, and sensitivity tests. Results: Histopathology studies indicated the absence of Munro's microabscess, regular elongation of rete ridges, capillary loop dilatation, granular cell layer, and prominent parakeratosis at 500 mg/kg. Formulations of the plant extracts did not reveal toxic components by GC-MS interpretation. No greasiness was observed during washing. Uniform homogeneity was observed with neither clumps nor large aggregates. The dispersed globules appeared red against colorless water background. Bleeding time was found to be stable during the experimentation.Conclusion: Developed topical plant formulations showed antipsoriatic potential on selected models. The GC-MS studies confirmed the presence of no drastic changes in the quantity of active constituents assuring its stability.

Repulsive Guidance Molecule A Regulates Adult Neurogenesis Via the Neogenin Receptor.

Repulsive guidance molecule A (RGMa) exhibits repulsive guidance of axonal growth and regulates neuronal differentiation during development of the mammalian brain. In this commentary, we describe the findings of our recent paper, “Repulsive Guidance Molecule A Suppresses Adult Neurogenesis,” and discuss a possible model for RGMa suppression of newborn neurons that fail to properly migrate into the granular cell layer. In the study, we provided evidence that RGMa suppressed neurite growth and survival of newborn neurons in the adult dentate gyrus. This effect depends on the multifunctional Neogenin receptor expressed in adult neural stem cells through activation of the Rho-associated protein kinase leading to neurite growth inhibition and ultimately cell death. It should be noted that both RGMa and Neogenin interact with several well-described molecules, including bone morphogenetic proteins, that regulate neuronal development. Thus, it is likely that RGMa interacts with other intricate molecular networks that regulate adult neurogenesis.

Harnessing neurogenesis in the adult brain-A role in type 2 diabetes mellitus and Alzheimer's disease.

Some metabolic disorders, such as type 2 diabetes mellitus (T2DM) are risk factors for the development of cognitive deficits and Alzheimer's disease (AD). Epidemiological studies suggest that in people with T2DM, the risk of developing dementia is 2.5 times higher than that in the non-diabetic population. The signaling pathways that underlie the increased risk and facilitate cognitive deficits are not fully understood. In fact, the cause of memory deficits in AD is not fully elucidated. The dentate gyrus of the hippocampus plays an important role in memory formation. Hippocampal neurogenesis is the generation of new neurons and glia in the adult brain throughout life. New neurons incorporate in the granular cell layer of the dentate gyrus and play a role in learning and memory and hippocampal plasticity. A large body of studies suggests that hippocampal neurogenesis is impaired in mouse models of AD and T2DM. Recent evidence shows that hippocampal neurogenesis is also impaired in human patients exhibiting mild cognitive impairment or AD. This review discusses the role of hippocampal neurogenesis in the development of cognitive deficits and AD, and considers inflammatory and endothelial signaling pathways in T2DM that may compromise hippocampal neurogenesis and cognitive function, leading to AD.

The distribution and density of monocarboxylate transporter 2 in cerebral cortex, hippocampus and cerebellum of wild-type mice.

Monocarboxylates cannot cross the blood-brain barrier freely to participate in brain energy metabolism. Specific monocarboxylate transporters (MCTs) are needed to cross cellular membranes. Monocarboxylate transporter 2 (MCT2) is a major monocarboxylate transporter encoded by the SLC16A7 gene. Recent studies reported that neurodegenerative diseases of the CNS, such as Alzheimer's disease (AD) and Parkinson's disease (PD), were related to energy metabolic impairment. MCT2 also plays an important role in energy metabolism in the CNS. To provide experimental evidence for future research on the role of MCT2 in the pathological process of CNS degenerative diseases, the distribution and density of MCT2 in different subregions of wild-type mouse brain was examined using immunohistochemistry, western blot and immunogold post-embedding electron microscopic techniques. The amount of MCT2 was higher in cerebellum than in cortex and hippocampus on western blots, and there was no statistical difference between cortex and hippocampus. Immunohistochemistry assay revealed the highest density of MCT2 in the CA3 of the hippocampus. The granular cell layer of the cerebellum contained more MCT2 than the molecular layer. The MCT2 density on the end feet of astrocytes of molecular layer was lower than in hippocampus, but the postsynaptic densities (PSDs) of asymmetric synapses in the molecular layer exhibited a high density using immunogold post-embedding electron microscopic techniques.

Neuronal precursor cells with dopaminergic commitment in the rostral migratory stream of the mouse

Neuroblasts born in the subventricular zone of adult mammals migrate via the rostral migratory stream into the granular cell layer or periglomerular layer of the olfactory bulb to differentiate into interneurons. To analyze if new neurons in the granular cell layer or periglomerular layer have different origins, we inserted a physical barrier into the rostral migratory stream, depleted cell proliferation with cytarabine infusions, labeled newborn cells with bromodeoxyuridine, and sacrificed mice after short-term (0, 2, or 14 days) or long-term (55 or 105 days) intervals. After short-term survival, the subventricular zone and rostral migratory stream rapidly repopulated with bromodeoxyuridine+ cells after cytarabine-induced depletion. Nestin, glial fibrillary acidic protein and the PAX6 were expressed in bromodeoxyuridine+ cells within the rostral migratory stream downstream of the physical barrier. After long-term survival after physical barrier implantation, bromodeoxyuridine+ neurons were significantly reduced in the granular cell layer, but bromodeoxyuridine+ and dopaminergic neurons in the periglomerular layer remained unaffected by the physical barrier. Thus, newborn neurons for the granular cell layer are mainly recruited from neural stem cells located in the subventricular zone, but new neurons for the periglomerular layer with dopaminergic predisposition can rise as well from neuronal stem or precursor cells in the rostral migratory stream.

Immunoreactivity of estrogen receptor alpha in brain and ovary of the short mackerel Rastrelliger brachysoma (Bleeker, 1851)

The reproductive physiology concerning the gonadotropin hormone (GTH) and its downstream target estrogen receptor alpha (ERα) is not well understood in the short mackerel Rastrelliger brachysoma, an economically important marine fish in Thailand. In this study, we tested the hypothesis that the expression of both GTH and ERα in the brain and ovary of R. brachysoma was as reported in other fish species. By applying immunohistochemical techniques, we identified the distribution of ERα-immunoreactive (ir) neurons in the brain and ovary of wild female R. brachysoma during the spawning season along with the distribution of GTHs-ir cells in the ovary. The nucleus lateralis tuberis in the diencephalon had a high number of ERα-ir neurons. In the mesencephalon, dense ERα-ir neuronal fibers were mainly found in the mesencephalic cells, stratum opticum, stratum fibrosum et griseum superficiale and stratum album centrale. Both the valvula and corpus cerebelli in the metencephalon contained ERα-ir neurons in granular and Purkinje cell layers as well as the molecular layer. The ERα-ir neurons were also observed in the medulla oblongata. In the ovary, weak ERα and moderate GTHs immunoreactivities were observed in follicular cells of oocytes in early and late vitellogenic stages. This information provides baseline data required to understand not only the activity of estrogen (E2) on the brain but also the regulatory mechanism of the hypothalamo-pituitary-ovarian axis of R. brachysoma.

Effect of adipose-derived mesenchymal stem cell transplantation on cyclophosphamide-induced ovarian damage in rats

To explore the effect of adipose-derived mesenchymal stem cells (ADMSCs) on ovarian damage induced by cyclophosphamide (CTX) and its mechanism. Methods: ADMSCs isolated from adipose tissue of female SD rats were cultured and divided into a blank group and a CTX group (n=15 in each group). CTX (75 mg/kg) was injected intraperitoneally to establish a model of ovarian damage in rats. A total of 45 female SD rats were also divided into 3 groups: Group A (15 rats, only injected intraperitoneally with 75 mg/kg CTX diluted with 1 mL 0.9% saline), Group B [15 rats, injected intraperitoneally with 75 mg/kg CTX diluted with 1 mL 0.9% saline, after 4 estrus cycles, injected 0.6 mL ADMSCs (6×105 cells) by the tail vein], and Group C [15 rats, injected intraperitoneally with 75 mg/kg CTX diluted with 1 mL 0.9% saline, after 4 estrus cycles, injected 40 mL ADMSCs (20 mL per side, 2×104 cells) in situ ovarian]. After 4 estrus cycles, the changes of quality of life, ponderal growth were recorded, the sex hormone levels [estradiol (E2), follicle-stimulating hormone (FSH)] were tested by ELISA, and the morphology of ovarian tissue and follicle count were observed by HE staining. The expression of BMP-15, Bcl-2 and Bax in ovarian tissues were tested by immunohistochemistry, real-time PCR or Western blotting. The apoptosis rate of follicular cells was detected by TdT-mediated dUTP nick end labeling (TUNEL) assay. Results: After transplantation of ADMSCs, compared with the Group A, their quality of life of rats in the Group B and C was improved, and the ponderal growth was increased (both P<0.01). Compared with the Group A, the serum E2 levels in the Group B and the Group C were increased (P<0.01, P<0.05), and the FSH levels in the Group B and C were decreased (both P<0.01). The granular cell layer, the number of corpus lutein and the count of various grade follicles were significantly increased, and many new follicles and mature oocytes were observed in the Group B and C. Compared with Group A, the count of primitive follicles, sinusoidal follicles, pre-ovulation follicles and total follicles, and pre-sinusoidal follicles were dramatically increased in the Group B. The follicle at all levels count was increased in the Group C than that in the Group A (all P<0.01). Comparing with the Group A, the expressions of BMP-15 and Bcl-2 were increased (all P<0.01), the expressions of Bax was decreased (both P<0.01), and the apoptosis rates of follicular cells were decreased in the Group B and C (both P<0.01). However, there was no difference between the Group B and the Group C in the above indexes (all P>0.05). Conclusion: ADMSCs transplantation can effectively repair ovarian damage induced by CTX in rats, which may be achieved by inhibiting mitochondrial apoptosis of granulosa cells.

Heterogeneity of GRIM-19 Expression in the Adult Mouse Brain.

Gene associated with retinoid-interferon-induced mortality-19 (GRIM-19) is a subunit of the mitochondrial respiratory chain complex I that has a significant effect on ATP production. The brain is particularly susceptible to ATP deficiency due to its limited energy storage capability and its high rate of oxygen consumption. Thus, GRIM-19 might be involved in regulating ATP level in the brain or cell death caused by several neurological disorders. To understand the physiological and pathophysiological roles of GRIM-19 in the brain, a thorough investigation of the neuroanatomic distribution of GRIM-19 in the normal brain is necessary. Therefore, the present study examined the distribution patterns of GRIM-19 in the adult C57BL/6 mouse brain using immunohistochemistry and identified cell types expressing GRIM-19 using double immunofluorescence staining. We found that GRIM-19 was ubiquitously but not homogenously expressed throughout the brain. GRIM-19 immunoreactivity was predominantly observed in neurons, but not in astrocytes, microglia, or oligodendrocytes under normal physiological conditions. Following transient global cerebral ischemia, GRIM-19-positive immunoreactivity was, however, observed in neurons as well as glial cells including astrocytes in the hippocampus. Furthermore, GRIM-19 was weakly expressed in the hippocampal subgranular zone, in which neural stem and progenitor cells are abundant, but highly expressed in the immature and mature neuronal cells in the granular cell layer of the normal brain, suggesting an inverse correlation between expression of GRIM-19 and stemness activity. Collectively, our study demonstrating widespread and differential distribution of GRIM-19 in the adult mouse brain contributes to investigating the functional and pathophysiological roles of this protein.

Upregulation of Neuronal VEGF in Experimental Cerebral Malaria Coincides with Disease Severity Biomarkers in Humans: A Novel Mechanism of Pathophysiology

Abstract Cerebral malaria (CM) is a deadly neurological complication of Plasmodium falciparum infection resulting in high mortality or severe cognitive deficit. Current therapeutics are highly ineffective, namely due to drug resistance and lack of mechanistic insight into pathophysiology. CM is characterized by VEGF upregulation, disruption of blood-brain barrier (BBB), vascular permeability, and severe edema detectable by MRI. Using small animal MRI and the established animal model of CM Plasmodium berghei ANKA, we recapitulate these features of human disease. Here we show that regions of brain permeability during CM as identified by T1-weighted gadolinium-enhanced and T2-weighted MRI coincide with VEGF mRNA upregulation. Regions of analysis include granular and glomerular cell layers of main olfactory bulb and superior medullary brainstem. We determined through RNA in situ hybridization that neurons are the major cell type responsible for the increased VEGF production during CM. Interestingly, we identified another cell type found to minimally upregulate VEGF in close proximity to these neurons. These VEGF expressing cells may play a role in support or induction of the neuronal response. Intriguingly, astrocytes show no VEGF upregulation during this pathology. Overall, these findings suggest a novel role for neuronal-VEGF in promoting CNS pathology, and a putative mechanism of BBB disruption and vascular permeability during CM.

The Effects of Vascular Cognitive Impairment on the Thickness of the Granular Cell Layer of the Dentate Gyrus within the Hippocampus in a Mouse Model

Vascular Cognitive Impairment (VCI) is a form of dementia, most prevalent after Alzheimer’s Disease. However, VCI remains the second leading cause for dementia because it restricts blood flow to the brain and there are currently no treatments. There has been a positive correlation between VCI and hippocampal atrophy reported. Diet such as deficiencies in folic acid, is a modifiable risk factor for neurodegeneration. In the present study, a mouse model of VCI was combined with a deficiency in folic acid to assess hippocampal morphology. Animals were split into 4 experimental groups where they were placed into a control diet (CD) or folic acid deficient diet (FADD), and later these animals either had microcoils implanted around their common carotid arteries to model VCI or a sham, control surgery. For hippocampal morphological analysis, the thickness of the granular cell layer of the dentate gyrus within the hippocampus was measured. It was hypothesized that a mouse model of VCI with microcoil treatment and reduced levels of folic acid would reduce blood flow, and increase cell death resulting in a reduced thickness of the granular cell layer within the dentate gyrus of the hippocampus. Our results show that thickness had an increasing trend in the in the FADD microcoil group. These data suggest that there may be an additional factor coming into play such as compensation by neural stem cells that needs to be further researched.

Chronic stress triggers divergent dendritic alterations in immature neurons of the adult hippocampus, depending on their ultimate terminal fields

Chronic stress, a suggested precipitant of brain pathologies, such as depression and Alzheimer’s disease, is known to impact on brain plasticity by causing neuronal remodeling as well as neurogenesis suppression in the adult hippocampus. Although many studies show that stressful conditions reduce the number of newborn neurons in the adult dentate gyrus (DG), little is known about whether and how stress impacts on dendritic development and structural maturation of these newborn neurons. We, herein, demonstrate that chronic stress impacts differentially on doublecortin (DCX)-positive immature neurons in distinct phases of maturation. Specifically, the density of the DCX-positive immature neurons whose dendritic tree reaches the inner molecular layer (IML) of DG is reduced in stressed animals, whereas their dendritic complexity is increased. On the contrary, no change on the density of DCX-positive neurons whose dendritic tree extends to the medial/outer molecular layer (M/OML) of the DG is found under stress conditions, whereas the dendritic complexity of these cells is diminished. In addition, DCX+ cells displayed a more complex and longer arbor in the dendritic compartments located in the granular cell layer of the DG under stress conditions; on the contrary, their dendritic segments localized into the M/OML were shorter and less complex. These findings suggest that the neuroplastic effects of chronic stress on dendritic maturation and complexity of DCX+ immature neurons vary based on the different maturation stage of DCX-positive cells and the different DG sublayer, highlighting the complex and dynamic stress-driven neuroplasticity of immature neurons in the adult hippocampus.

Spatially restricted long-term transgene expression in the developing skin used for studying the interaction of epidermal development and sensory innervation.

Skin development is tightly temporally coordinated with its sensory innervation, which consists of the peripheral branches of the dorsal root ganglion (DRG) axons. Various studies suggest that the skin produces a long-range attractant for the sensory axons. However, the exact identity of the guidance cue(s) remains unclear. To reveal the detailed molecular mechanism that controls DRG axon guidance and targeting, manipulation of specific skin layers at specific time points are required. To test a variety of attractants that can be expressed in specific skin layers at specific timepoints, we combined in utero electroporation with the Tol2 transposon system to induce long-term transgene expression in the developing mouse skin, including in the highly proliferative epidermal stem cells (basal layer) and their descendants (spinous and granular layer cells). The plasmid solution was injected as close to the hindpaw plantar surface as possible. Immediately, electric pulses were passed through the embryo to transduce the plasmid DNA into hindpaw skin cells. Balancing outcome measurements including: embryo survival, transfection efficiency, and the efficiency of transgene integration into host cells, we found that IUE was best performed on E13.5, and using an electroporation voltage of 34V. After immunostaining embryonic and early postnatal skin tissue sections for keratinocyte and sensory axon markers, we observe the growth of axons into skin epidermal layers including areas expressing EGFP. Therefore, this method is useful for studying the interaction between axon growth and epidermal cell division/differentiation.

Female mice with apolipoprotein E4 domain interaction demonstrated impairments in spatial learning and memory performance and disruption of hippocampal cyto-architecture.

We have previously reported cognitive impairments in both young and old mice, particularly in female mice expressing mouse Arg-61 apoE, with a point mutation to mimic the domain interaction feature of human apoE4, as compared to the wildtype mouse (C57BL/6J) apoE. In this study, we further evaluated water maze performance in the female Arg-61 mice at an additional time point and then investigated related hippocampal cyto-architecture in these young female Arg-61 apoE mice vs. the wildtype mice. The results of behavioral performance consistently support our previous report that the young female Arg-61 apoE showed cognitive impairment versus C57BL/6J at the same age. The cyto-architectural results showed that volume of the granular cell layer (GCL) was significantly larger in both 5- and 10-month old Arg-61 apoE mice versus C57BL/6J mice. While the number of newborn calretinin-positive neurons was greater in the sub-granular zone (SGZ) in 5-month old Arg-61 mice, this number dropped significantly in 10-month old Arg-61 mice to a lower level than in age-matched C57BL/6J mice. In addition, the amyloid β species was significantly higher in 5-month old Arg-61 mice versus age-matched C57BL/6J mice. In conclusion, impaired cognitive functions in female Arg-61 apoE mice appear correlated with larger GCL volume and higher calretinin-positive cell number and suggest a compensatory cellular response that may be related to amyloid beta perturbations early in life. Therefore this study suggests a novel cyto-architectural mechanism of apoE4-dependent pathologies and increased susceptibility of APOEε4 subjects to Alzheimer's disease.

Valproic Acid Leads New Neurons Down the Wrong Path.

Ectopic Neurogenesis Induced by Prenatal Antiepileptic Drug Exposure Augments Seizure Susceptibility in Adult Mice Sakai A, Matsuda T, Doi H, Nagaishi Y, Kato K, Nakashima K. Proc Natl Acad Sci U S A. 2018;115(16):4270-4275. doi:10.1073/pnas.1716479115Epilepsy is a neurological disorder often associated with seizure that affects ∼0.7% of pregnant women. During pregnancy, most epileptic patients are prescribed antiepileptic drugs (AEDs) such as valproic acid (VPA) to control seizure activity. Here, we show that prenatal exposure to VPA in mice increases seizure susceptibility in adult offspring through mislocalization of newborn neurons in the hippocampus. We confirmed that neurons newly generated from neural stem/progenitor cells (NS/PCs) are integrated into the granular cell layer in the adult hippocampus; however, prenatal VPA treatment altered the expression in NS/PCs of genes associated with cell migration, including CXC motif chemokine receptor 4 (Cxcr4), consequently increasing the ectopic localization of newborn neurons in the hilus. We also found that voluntary exercise in a running wheel suppressed this ectopic neurogenesis and countered the enhanced seizure susceptibility caused by prenatal VPA exposure, probably by normalizing the VPA-disrupted expression of multiple genes including Cxcr4 in adult NS/PCs. Replenishing Cxcr4 expression alone in NS/PCs was sufficient to overcome the aberrant migration of newborn neurons and increased seizure susceptibility in VPA-exposed mice. Thus, prenatal exposure to an AED, VPA, has a long-term effect on the behavior of NS/PCs in offspring, but this effect can be counteracted by a simple physical activity. Our findings offer a step to developing strategies for managing detrimental effects in offspring exposed to VPA in utero.

Histoarchitecture restoration of cerebellar sub-layers as a response to estradiol treatment following Kainic acid-induced spinal cord injury.

One of the major impacts of spinal cord injury (SCI) is the cerebellar neurological malfunction and deformation of its sub-layers. This could be due to the enormous innervation of the spinocerebellar tract from the posterior gray horn in the spinal cord to the ipsilateral cerebellum. Although the neuroprotective role of estradiol in spinal cord (SC) injuries, as well as its ability to delay secondary cell death changes, is well-known, its effect on cerebellar layers is not fully investigated. In this study, a SCI model was achieved by injection of Kainic acid into SC of adult Male Wistar rats in order to assess the effects of SCI on the cerebellum. The animals were classified into SCI group (animals with SCI), estradiol-treated group (animals with SCI and received estradiol), control groups, and sham control group. The microscopical examination 24h after induction of SCI revealed that KA induced the most characteristics of neurodegeneration including astrocytic propagation and microglial activation. The estradiol was injected intraperitoneally 20min after induction of SCI, and the samples were collected at 1, 3, 7, 14, and 30days. Histologically, the estradiol reduced the inflammatory response, enhanced the recovery of molecular, granular, and Purkinje cell layers, and therefore aided in the restoration of layer organization. These findings were also confirmed by immunohistochemical staining and gene expression profiling.

The possible protective effect of Gardenia Jasminoides extracts on the dentate gyrus changes in an Alzheimer-induced model in adult male albino rats: Histological and Immunohistochemical study

Introduction: Alzheimer's disease (AD) is the most common diagnosed form of senile dementias, a neurodegenerative disease resulting in cognitive impairment in the elderly. Geniposide, extracted of Gardenia Jasminoides, is widely used herb for brain diseases and reduce amyloid plaques deposition which is an intricate process in AD.Aim of the work: demonstrate the histological changes in the dentate gyrus of hippocampus in an Alzheimer-induced model and the possible neuroprotective effect of Gardenia Jasminoides extract.Materials and methods: Thirty six adult male albino rats(4-6 months) , weighing180-200g divided into 3 groups. Group I the control group, group II given aluminum chloride dissolved in distilled water, (300mg/kg/day) orally for one month. Group (III) given Geniposide in distilled water,at a dose of (100mg/kg/day) orally concomitant with aluminum chloride at the same dose and period of the previous group. Cognitive functions were assessed by the passive avoidance test. Temporal lobes processed for H&E , congo red stains. Immunohistochemical study for detection of (GFAP) and (INOS). Tau protein can be phosphorylated by glycogen synthase Kinase-3β(GSK-3 β). Western blot assay to investigate the total protein expression glycogen synthase Kinase-3β(GSK-3 β) . Comet assay to detect DNA damage.Results: Alzheimer-induced model group showed significantly impaired cognitive performance which was improved after treatment with Geniposide extract. Changes in the dentate gyrus apparent increase in immature neurons, disturbed granular cell layer, distortion of pyramidal cells that appeared with pyknotic nuclei. Positive immunoreaction for GFAP in astrocytes were also observed. The ultra structural study exhibited neurons with apoptotic features, heterochromatic nuclei and their cytoplasm contained dilated cisternae of rough endoplasmic reticulum. Gardenia extracts ameliorated histological alterations.Conclusion: Gardenia Jasminoides extracts significantly ameliorated the neuro- degenerative alterations induced in the Alzheimer model. Daily supplements of Gardenia Jasminoides extracts might be of benefit for the elderly people at risk of developing AD.

Enduring effects of muscarinic receptor activation on adult hippocampal neurogenesis, microRNA expression and behaviour

The cholinergic system is one of the most important neurotransmitter systems in the brain with key roles in autonomic control and the regulation of cognitive and emotional responses. However, the precise mechanism by which the cholinergic system influences behaviour is unclear. Adult hippocampal neurogenesis (AHN) is a potential mediator in this context based on evidence, which has identified this process as putative mechanism of antidepressant action. More recently, post-transcriptional regulation by microRNAs is another candidate mechanism based on its involvement in the regulation of AHN and neurotransmission. Taking into account this background, we evaluated the behavioural effects of a non-convulsant dose of pilocarpine - a non-selective muscarinic receptor (mAChR) agonist – in adult Wistar rats. Furthermore, we quantified the expression of different microRNAs implicated in the regulation of AHN. Our results suggests that pilocarpine treatment increases AHN in the granular cell layer but also induced ectopic neurogenesis. Pilocarpine treatment reduced immobility time in forced swimming test but did not affect fear conditioning response, sucrose preference or novelty supressed feeding behaviour. In addition, treatment with pilocarpine down-regulated the expression of 6 microRNAs implicated in the regulation of neurotrophin signalling and axon guidance pathways. Therefore, we suggest that the low-dose stimulation of the cholinergic system is sufficient to alter AHN of rats through post-transcriptional mechanisms, which might contribute to long-lasting behavioural effects.

Differential expression of genes in the subgranular zone and granular cell layer of the hippocampus after running.

[Purpose]Despite numerous studies, the mechanisms underlying the effects of exercise on brain function are not yet fully understood. Adult hippocampal neurogenesis is one of the most well-known effects of exercise on the brain, but its physiological roles during exercise are still ambiguous, mostly due to the difference in the structure and composition of each part of the hippocampus.[Methods]In this study, we analyzed exercise-induced changes in gene expression in the subgranular zone (SGZ) and granular cell layer (GCL) of the hippocampus.[Results]Surprisingly, only about 10% of changes were common to both areas. Tollip expression, which is altered in the SGZ and in Engrailed-2 mutant mice following exercise, did not change in the GCL. Tollip levels were not changed in the whole hippocampus after two weeks of treadmill exercise, but immunofluorescence analysis showed that Tollip and Ki-67 co-localize in the hippocampal dentate gyrus . Through siRNA knockdown experiments, we found that levels of DCX and cellular survival rates were decreased in Tollip-deficient Neuro2A cells.[Conclusion]Taken together, these results suggest a role for Tollip in mediating the beneficial effects of exercise, probably affecting cellular health in the SGZ of the hippocampus.

Melatonin Influences Structural Plasticity in the Axons of Granule Cells in the Dentate Gyrus of Balb/C Mice.

Melatonin, the main product synthesized by the pineal gland, acts as a regulator of the generation of new neurons in the dentate gyrus (DG). Newborn neurons buffer the deleterious effects of stress and are involved in learning and memory processes. Furthermore, melatonin, through the regulation of the cytoskeleton, favors dendrite maturation of newborn neurons. Moreover, newborn neurons send their axons via the mossy fiber tract to Cornu Ammonis 3 (CA3) region to form synapses with pyramidal neurons. Thus, axons of newborn cells contribute to the mossy fiber projection and their plasticity correlates with better performance in several behavioral tasks. Thus, in this study, we analyzed the impact of exogenous melatonin (8 mg/kg) administered daily for one- or six-months on the structural plasticity of infrapyramidal- and suprapyramidal mossy fiber projection of granule cells in the DG in male Balb/C mice. We analyzed the mossy fiber projection through the staining of calbindin, that is a calcium-binding protein localized in dendrites and axons. We first found an increase in the number of calbindin-positive cells in the granular cell layer in the DG (11%, 33%) after treatment. Futhermore, we found an increase in the volume of suprapyramidal (>135%, 59%) and infrapyramidal (>128%, 36%) mossy fiber projection of granule neurons in the DG after treatment. We also found an increase in the volume of CA3 region (>146%, 33%) after treatment, suggesting that melatonin modulates the structural plasticity of the mossy fiber projection to establish functional synapses in the hippocampus. Together, the data suggest that, in addition to the previously reported effects of melatonin on the generation of new neurons and its antidepressant like effects, melatonin also modulates the structural plasticity of axons in granule cells in the DG.

ADAMTS18 Deficiency Affects Neuronal Morphogenesis and Reduces the Levels of Depression-like Behaviors in Mice

The ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) enzymes are secreted, multi-domain matrix-associated zinc metalloendopeptidases that modify extracellular matrix components and play crucial roles in development and numerous diseases. ADAMTS18 is a member of the ADAMTS family, and genome-wide association studies made an initial association of ADAMTS18 with white matter integrity in healthy people of 72–74 years old. However, the potential roles of ADAMTS18 in central nervous system remain unclear. In this study, we showed that Adamts18 mRNA is highly abundant in developing brains, especially in the cerebellum granular cell layer and the hippocampus dentate gyrus (DG) granular cell layer. Adamts18 knockout (KO) mice displayed higher dendritic branching complexity and spine density on hippocampal DG granular cells. Behavioral tests showed that Adamts18 KO mice had reduced levels of depression-like behaviors compared to their wild-type (WT) littermates. The increased neurite formation could be attributed in part to reduced phosphorylation levels of the collapsin response mediator protein-2 (CRMP2) due to activation of the laminin/PI3K/AKT/GSK-3β signaling pathway. Our findings revealed a critical role of ADAMTS18 in neuronal morphogenesis and emotional control in mice.