Polysialylation of NCAM is upregulated by hyperthermia and participates in heat shock preconditioning-induced neuroprotection

Acute Sleep Deprivation-Induced Anxiety and Disruption of Hypothalamic Cell Survival and Plasticity: A Mechanistic Study of Protection by Butanol Extract of Tinospora cordifolia

Since sleep is a key homeostatic phenomenon of the body, therefore understanding the complex etiology of the neurological outcome of sleep deprivation (SD) such as anxiety, depression, cognitive dysfunctions, and their management is of utmost importance. The findings of the current study encompass the neurobehavioral as well as hormonal, and neuroinflammatory changes in serum and hypothalamus region of the brain as an outcome of acute SD and their amelioration by pre-treatment with butanol extract of Tinospora cordifolia. SD group animals showed anxiety-like behavior as evident from Elevated Plus Maze data and higher serum cortisol levels, whereas, pre-treatment with B-TCE showed anxiolytic activity and also reduced cortisol levels which was corroborated by an increase in leptin and insulin levels. Further, SD induced elevation of serum pro-inflammatory cytokines IL-6, TNF-α, IL-1β, and MCP-1 and subsequent activation of astroglial cells in the hypothalamus was suppressed in B-TCE pre-treated animals. The current findings suggest that besides the cortical structures, hypothalamus region's synaptic plasticity and cell survival are adversely impacted by acute SD. Further active ingredients present in B-TCE may be useful for the management of SD-induced anxiety, systemic inflammation, and neuroinflammation by targeting hypothalamic BDNF-TrkB/PI3K-Akt pathways.

Cognitive Effects of Astaxanthin Pretreatment on Recovery From Traumatic Brain Injury

Traumatic brain injury (TBI), caused by mechanical impact to the brain, is a leading cause of death and disability among young adults, with slow and often incomplete recovery. Preemptive treatment strategies may increase the injury resilience of high-risk populations such as soldiers and athletes. In this work, the xanthophyll carotenoid Astaxanthin was examined as a potential nutritional preconditioning method in mice (sabra strain) to increase their resilience prior to TBI in a closed head injury (CHI) model. The effect of Astaxanthin pretreatment on heat shock protein (HSP) dynamics and functional outcome after CHI was explored by gavage or free eating (in pellet form) for 2 weeks before CHI. Assessment of neuromotor function by the neurological severity score (NSS) revealed significant improvement in the Astaxanthin gavage-treated group (100 mg/kg, ATX) during recovery compared to the gavage-treated olive oil group (OIL), beginning at 24 h post-CHI and lasting throughout 28 days (p < 0.007). Astaxanthin pretreatment in pellet form produced a smaller improvement in NSS vs. posttreatment at 7 days post-CHI (p < 0.05). Cognitive and behavioral evaluation using the novel object recognition test (ORT) and the Y Maze test revealed an advantage for Astaxanthin administration via free eating vs. standard chow during recovery post-CHI (ORT at 3 days, p < 0.035; improvement in Y Maze score from 2 to 29 days, p < 0.02). HSP profile and anxiety (open field test) were not significantly affected by Astaxanthin. In conclusion, astaxanthin pretreatment may contribute to improved recovery post-TBI in mice and is influenced by the form of administration.

Aqueous Leaf Extract of Withania somnifera as a Potential Neuroprotective Agent in Sleep-deprived Rats: a Mechanistic Study

Modern lifestyle and sustained stress of professional commitments in the current societal set up often disrupts the normal sleep cycle and duration which is known to lead to cognitive impairments. In the present study, we report whether leaf extract of Withania somnifera (Ashwagandha) has potential neuroprotective role in acute stress of sleep deprivation. Experiments were performed on three groups of adult Wistar rats: group 1 (vehicle treated-undisturbed sleep [VUD]), group 2 (vehicle treated-sleep deprived [VSD]), and group 3 (ASH-WEX treated-sleep deprived [WSD]). Groups 1 and 2 received single oral feeding of vehicle and group 3 received ASH-WEX orally (140 mg/kg or 1 ml/250 g of body weight) for 15 consecutive days. Immediately after this regimen, animals from group 1 were allowed undisturbed sleep (between 6 a.m. and 6 p.m.), whereas rats of groups 2 and 3 were deprived of sleep during this period. We observed that WSD rats showed significant improvement in their performance in behavioral tests as compared to VSD group. At the molecular level, VSD rats showed acute change in the expression of proteins involved in synaptic plasticity, cell survival, and apoptosis in the hippocampus region of brain, which was suppressed by ASH-WEX treatment thus indicating decreased cellular stress and apoptosis in WSD group. This data suggest that Ashwagandha may be a potential agent to suppress the acute effects of sleep loss on learning and memory impairments and may emerge as a novel supplement to control SD-induced cognitive impairments.

Efficient neuronal in vitro and in vivo differentiation after immunomagnetic purification of mESC derived neuronal precursors

The cellular heterogeneity that is generated during the differentiation of pluripotent stem cells into specific neural subpopulations represents a major obstacle for experimental and clinical progress. To address this problem we developed an optimized strategy for magnetic isolation of PSA-NCAM positive neuronal precursors from embryonic stem cells (ESCs) derived neuronal cultures. PSA-NCAM enrichment at an early step of the in vitro differentiation process increased the number of ES cell derived neurons and reduced cellular diversity. Gene expression analysis revealed that mainly genes involved in neuronal activity were over-represented after purification. In vitro derived PSA-NCAM(+) enriched precursors were characterized in vivo through grafting into the forebrain of adult mice. While unsorted control cells 40 days post graft gave rise to a mixed population composed of immature precursors, early postmitotic neurons and glial cells, PSA-NCAM(+) enriched cells differentiated predominantly into NeuN positive cells. Furthermore, PSA-NCAM enriched population showed efficient migration towards the olfactory bulb after transplantation into the rostral migratory stream of the forebrain neurogenic system. Thus, enrichment of neuronal precursors based on PSA-NCAM expression represents a general and straightforward approach to narrow cellular heterogeneity during neuronal differentiation of pluripotent cells.

Mouse brain PSA-NCAM levels are altered by graded-controlled cortical impact injury

Traumatic brain injury (TBI) is a worldwide endemic that results in unacceptably high morbidity and mortality. Secondary injury processes following primary injury are composed of intricate interactions between assorted molecules that ultimately dictate the degree of longer-term neurological deficits. One comparatively unexplored molecule that may contribute to exacerbation of injury or enhancement of recovery is the posttranslationally modified polysialic acid form of neural cell adhesion molecule, PSA-NCAM. This molecule is a critical modulator of central nervous system plasticity and reorganization after injury. In this study, we used controlled cortical impact (CCI) to produce moderate or severe TBI in the mouse. Immunoblotting and immunohistochemical analysis were used to track the early (2, 24, and 48 hour) and late (1 and 3 week) time course and location of changes in the levels of PSA-NCAM after TBI. Variable and heterogeneous short- and long-term increases or decreases in expression were found. In general, alterations in PSA-NCAM levels were seen in the cerebral cortex immediately after injury, and these reductions persisted in brain regions distal to the primary injury site, especially after severe injury. This information provides a starting point to dissect the role of PSA-NCAM in TBI-related pathology and recovery.

Water extract from the leaves of Withania somnifera protect RA differentiated C6 and IMR-32 cells against glutamate-induced excitotoxicity

Glutamate neurotoxicity has been implicated in stroke, head trauma, multiple sclerosis and neurodegenerative disorders. Search for herbal remedies that may possibly act as therapeutic agents is an active area of research to combat these diseases. The present study was designed to investigate the neuroprotective role of Withania somnifera (Ashwagandha), also known as Indian ginseng, against glutamate induced toxicity in the retinoic acid differentiated rat glioma (C6) and human neuroblastoma (IMR-32) cells. The neuroprotective activity of the Ashwagandha leaves derived water extract (ASH-WEX) was evaluated. Cell viability and the expression of glial and neuronal cell differentiation markers was examined in glutamate challenged differentiated cells with and without the presence of ASH-WEX. We demonstrate that RA-differentiated C6 and IMR-32 cells, when exposed to glutamate, undergo loss of neural network and cell death that was accompanied by increase in the stress protein HSP70. ASH-WEX pre-treatment inhibited glutamate-induced cell death and was able to revert glutamate-induced changes in HSP70 to a large extent. Furthermore, the analysis on the neuronal plasticity marker NCAM (Neural cell adhesion molecule) and its polysialylated form, PSA-NCAM revealed that ASH-WEX has therapeutic potential for prevention of neurodegeneration associated with glutamate-induced excitotoxicty.

The Injured and Regenerating Nervous System

Understanding restricted functional recovery and designing efficient treatments to alleviate dysfunction after injury of the nervous system remain major challenges in neuroscience and medicine. Numerous molecules of potential significance in neural repair have been identified in vitro, but only few of these have proved to be of major importance in vivo up to now. Among the molecules involved in regeneration are several members of the immunoglobulin superfamily, most notably the neural cell adhesion molecules L1, its close homologue CHL1, and NCAM and, in particular, its polysialic acid glycan moiety. Sufficient evidence is now available to justify the statement that these molecules are major players not only in nervous system development but also in the adult during neural repair and synaptic plasticity. Importantly, insights into the functions of these molecules in promoting or inhibiting functional recovery have allowed the design and assessment of therapeutic approaches in animal models of central nervous system injury that could prove to be applicable in clinical settings.

Hyperthermia conditioned astrocyte-cultured medium protects neurons from ischemic injury by the up-regulation of HIF-1 alpha and the increased anti-apoptotic ability

It has been demonstrated that conditioned medium from astrocytes challenged by in vitro ischemia (oxygen-glucose deprivation, OGD) improved neuronal survival. In addition, preconditioning stimuli can be cross-tolerant, safeguarding against other types of injury. We therefore hypothesized that hyperthermia-conditioned astrocyte-cultured medium (ACM) might also have protective effect on neurons against ischemic injury. The cultured-media, named 38ACM and 40ACM respectively, were collected after astrocytes had been incubated at 38 °C or 40 °C for 6h, followed by incubation at 37 °C for 24h. It was found that ischemia for 6h induced a significant reduction in the number of neuronal cells and cell-viability, and an increase in lactate dehydrogenase (LDH) release and the percentage of apoptotic nuclei in neurons. Pre-treatment with 38ACM or 40ACM for 24h significantly diminished ischemia injury, enhanced cell viability, reduced LDH release and reversed apoptosis. Western blot analysis showed that treatment with 38ACM or 40ACM for 24h led to a significant increase in hypoxia-inducible factor-1 (HIF-1) alpha expression. The EMSA demonstrated that the ACM increased the binding activity of HIF-1 in ischemic neurons. The data implied that hyperthermia-conditioned ACM protects neurons from ischemic injury by up-regulating HIF-1 alpha, and the increased binding activity of HIF-1 and anti-apoptotic ability.

H3 receptor antagonism enhances NCAM PSA-mediated plasticity and improves memory consolidation in odor discrimination and delayed match-to-position paradigms

To further understand the procognitive actions of GSK189254, a histamine H(3) receptor antagonist, we determined its influence on the modulation of hippocampal neural cell adhesion molecule (NCAM) polysialylation (PSA) state, a necessary neuroplastic mechanism for learning and memory consolidation. A 4-day treatment with GSK189254 significantly increased basal expression of dentate polysialylated cells in rats with the maximal effect being observed at 0.03-0.3 mg/kg. At the optimal dose (0.3 mg/kg), GSK189254 enhanced water maze learning and the associated transient increase in NCAM-polysialylated cells. The increase in dentate polysialylated cell frequency induced by GSK189254 was not attributable to enhanced neurogenesis, although it did induce a small, but significant, increase in the survival of these newborn cells. GSK189254 (0.3 mg/kg) was without effect on polysialylated cell frequency in the entorhinal and perirhinal cortex, but significantly increased the diffuse PSA staining observed in the anterior, ventromedial, and dorsomedial aspects of the hypothalamus. Consistent with its ability to enhance the learning-associated, post-training increases in NCAM PSA state, GSK189254 (0.3 mg/kg) reversed the amnesia induced by scopolamine given in the 6-h post-training period after training in an odor discrimination paradigm. Moreover, GSK189254 significantly improved the performance accuracy of a delayed match-to-position paradigm, a task dependent on the prefrontal cortex and degree of cortical arousal, the latter may be related to enhanced NCAM PSA-associated plasticity in the hypothalamus. The procognitive actions of H3 antagonism combined with increased NCAM PSA expression may exert a disease-modifying action in conditions harboring fundamental deficits in NCAM-mediated neuroplasticity, such as schizophrenia and Alzheimer's disease.

Curcumin-induced degradation of PKC delta is associated with enhanced dentate NCAM PSA expression and spatial learning in adult and aged Wistar rats

Polysialylation of the neural cell adhesion molecule (NCAM PSA) is necessary for the consolidation processes of hippocampus-based learning. Previously, we have found inhibition of protein kinase C delta (PKCdelta) to be associated with increased polysialyltransferase (PST) activity, suggesting inhibitors of this kinase might ameliorate cognitive deficits. Using a rottlerin template, a drug previously considered an inhibitor of PKCdelta, we searched the Compounds Available for Purchase (CAP) database with the Accelrys((R)) Catalyst programme for structurally similar molecules and, using the available crystal structure of the phorbol-binding domain of PKCdelta, found that diferuloylmethane (curcumin) docked effectively into the phorbol site. Curcumin increased NCAM PSA expression in cultured neuro-2A neuroblastoma cells and this was inversely related to PKCdelta protein expression. Curcumin did not directly inhibit PKCdelta activity but formed a tight complex with the enzyme. With increasing doses of curcumin, the Tyr(131) residue of PKCdelta, which is known to direct its degradation, became progressively phosphorylated and this was associated with numerous Tyr(131)-phospho-PKCdelta fragments. Chronic administration of curcumin in vivo also increased the frequency of polysialylated cells in the dentate infragranular zone and significantly improved the acquisition and consolidation of a water maze spatial learning paradigm in both adult and aged cohorts of Wistar rats. These results further confirm the role of PKCdelta in regulating PST and NCAM PSA expression and provide evidence that drug modulation of this system enhances the process of memory consolidation.

Polysialylated-neural cell adhesion molecule (PSA-NCAM) in the human trigeminal ganglion and brainstem at prenatal and adult ages

Background

The polysialylated neuronal cell adhesion molecule (PSA-NCAM) is considered a marker of developing and migrating neurons and of synaptogenesis in the immature vertebrate nervous system. However, it persists in the mature normal brain in some regions which retain a capability for morphofunctional reorganization throughout life. With the aim of providing information relevant to the potential for dynamic changes of specific neuronal populations in man, this study analyses the immunohistochemical occurrence of PSA-NCAM in the human trigeminal ganglion (TG) and brainstem neuronal populations at prenatal and adult age.

Results

Western blot analysis in human and rat hippocampus supports the specificity of the anti-PSA-NCAM antibody and the immunodetectability of the molecule in postmortem tissue. Immunohistochemical staining for PSA-NCAM occurs in TG and several brainstem regions during prenatal life and in adulthood. As a general rule, it appears as a surface staining suggestive of membrane labelling on neuronal perikarya and proximal processes, and as filamentous and dot-like elements in the neuropil. In the TG, PSA-NCAM is localized to neuronal perikarya, nerve fibres, pericellular networks, and satellite and Schwann cells; further, cytoplasmic perikaryal staining and positive pericellular fibre networks are detectable with higher frequency in adult than in newborn tissue. In the adult tissue, positive neurons are mostly small- and medium-sized, and amount to about 6% of the total ganglionic population. In the brainstem, PSA-NCAM is mainly distributed at the level of the medulla oblongata and pons and appears scarce in the mesencephalon. Immunoreactivity also occurs in discretely localized glial structures. At all ages examined, PSA-NCAM occurs in the spinal trigeminal nucleus, solitary nuclear complex, vestibular and cochlear nuclei, reticular formation nuclei, and most of the precerebellar nuclei. In specimens of different age, the distribution pattern remains fairly steady, whereas the density of immunoreactive structures and the staining intensity may change and are usually higher in newborn than in adult specimens.

Conclusion

The results obtained show that, in man, the expression of PSA-NCAM in selective populations of central and peripheral neurons occurs not only during prenatal life, but also in adulthood. They support the concept of an involvement of this molecule in the structural and functional neural plasticity throughout life. In particular, the localization of PSA-NCAM in TG primary sensory neurons likely to be involved in the transmission of protopathic stimuli suggests the possible participation of this molecule in the processing of the relevant sensory neurotransmission.

Age-related impairments in neuronal plasticity markers and astrocytic GFAP and their reversal by late-onset short term dietary restriction

Recent studies on the effects of dietary restriction (DR) in rodents and primates have shown that even late-onset short-term regimens can bring about comparable beneficial changes seen in animals subjected to life-long DR. We studied the effect of aging on the expression of neural cell adhesion molecule (NCAM), its polysialylated form PSA-NCAM and astrocytic marker glial fibrillary acidic protein (GFAP) by immunohistofluorescent staining and immunoblotting in 1, 3, 6, 18 and 24 months old male wistar rats. Maximum expression of NCAM and PSA-NCAM was observed in sub-granular zone (SGZ) or granular cell layer (GCL) of hippocampus, arcuate region and paraventricular area of hypothalamus and piriform cortex layer II from 1 and 3 months old rats, thereafter, gradual downregulation was observed in 6, 18 and 24 months old rats. Progressive increase in astrocytic GFAP expression was noticed in these regions of brain with age. We further addressed whether DR initiated in late adulthood in 24 months old rats confers beneficial effects and can reverse changes in expression of NCAM, PSA-NCAM and GFAP. These results suggest that even late-onset short term DR regimen in old rats can have beneficial effects on neuroplasticity.