Interplay between biochemical processes and network properties generates neuronal up and down states at the tripartite synapse.

Neuronal up and down states have long been known to exist both in vitro and in vivo. A variety of functions and mechanisms have been proposed for their generation, but there has not been a clear connection between the functions and mechanisms. We explore the potential contribution of cellular-level biochemistry to the network-level mechanisms thought to underlie the generation of up and down states. We develop a neurochemical model of a single tripartite synapse, assumed to be within a network of similar tripartite synapses, to investigate possible function-mechanism links for the appearance of up and down states. We characterize the behavior of our model in different regions of parameter space and show that resource limitation at the tripartite synapse affects its ability to faithfully transmit input signals, leading to extinction-down states. Recovery of resources allows for "reignition" into up states. The tripartite synapse exhibits distinctive "regimes" of operation depending on whether ATP, neurotransmitter (glutamate), both, or neither, is limiting. Our model qualitatively matches the behavior of six disparate experimental systems, including both in vitro and in vivo models, without changing any model parameters except those related to the experimental conditions. We also explore the effects of varying different critical parameters within the model. Here we show that availability of energy, represented by ATP, and glutamate for neurotransmission at the cellular level are intimately related, and are capable of promoting state transitions at the network level as ignition and extinction phenomena. Our model is complementary to existing models of neuronal up and down states in that it focuses on cellular-level dynamics while still retaining essential network-level processes. Our model predicts the existence of a "final common pathway" of behavior at the tripartite synapse arising from scarcity of resources and may explain use dependence in the phenomenon of "local sleep." Ultimately, sleeplike behavior may be a fundamental property of networks of tripartite synapses.

Potential treatment of Parkinson's disease with omega-3 polyunsaturated fatty acids.

Parkinson's disease (PD) is characterized by dysfunction of the nigrostriatal system, loss of dopamine neurons and intracellular aggregation of α-synuclein. Recently, both clinical and experimental studies have reported that neuroinflammation and oxidative stress markedly contribute to the etiology of PD. Current clinical pharmacotherapies only temporarily relieve the symptoms of PD, accompanied by many side effects. Hence, searching for natural anti-inflammatory, anti-oxidative and neuroprotective agents has received great attention. Polyunsaturated fatty acids (PUFAs), especially omega (n)-3, are essential lipid nutrients in the human diet and important components of cell membranes. Together by competing with the production of n-6 PUFAs, the precursors of inflammatory mediators, n-3 PUFAs can inhibit microglial activity and neuroinflammation, protect astrocyte function to produce neurotrophins, thereby normalizing neurotransmission and improving neurodegeneration. Thus, with regard to the hypotheses of PD, our and other's recent studies have demonstrated that n-3 PUFAs may improve PD by inhibiting proinflammatory cytokine release, promoting neurotrophic factor expression, recovering mitochondrial function and membrane fluidity, decreasing the levels of oxidant production, maintaining α-synuclein proteostasis, calcium homeostasis, axonal transport, and reducing endoplasmic reticulum stress. This review mainly introduces and analyzes the effect of n-3 PUFA treatments on PD-related behavioral and neuropathological abnormalities in clinical patients and different cellular and animal models of PD. Finally, the limitations and future work in n-3 PUFAs anti-PD area are discussed.

Korean Red Ginseng Improves Astrocytic Mitochondrial Function by Upregulating HO-1-Mediated AMPKα-PGC-1α-ERRα Circuit after Traumatic Brain Injury.

Heme oxygenase-1 (HO-1) exerts beneficial effects, including angiogenesis and energy metabolism via the peroxisome proliferator-activating receptor-γ coactivator-1α (PGC-1α)-estrogen-related receptor α (ERRα) pathway in astrocytes. However, the role of Korean red ginseng extract (KRGE) in HO-1-mediated mitochondrial function in traumatic brain injury (TBI) is not well-elucidated. We found that HO-1 was upregulated in astrocytes located in peri-injured brain regions after a TBI, following exposure to KRGE. Experiments with pharmacological inhibitors and target-specific siRNAs revealed that HO-1 levels highly correlated with increased AMP-activated protein kinase α (AMPKα) activation, which led to the PGC-1α-ERRα axis-induced increases in mitochondrial functions (detected based on expression of cytochrome c oxidase subunit 2 (MTCO2) and cytochrome c as well as O2 consumption and ATP production). Knockdown of ERRα significantly reduced the p-AMPKα/AMPKα ratio and PGC-1α expression, leading to AMPKα-PGC-1α-ERRα circuit formation. Inactivation of HO by injecting the HO inhibitor Sn(IV) protoporphyrin IX dichloride diminished the expression of p-AMPKα, PGC-1α, ERRα, MTCO2, and cytochrome c in the KRGE-administered peri-injured region of a brain subjected to TBI. These data suggest that KRGE enhanced astrocytic mitochondrial function via a HO-1-mediated AMPKα-PGC-1α-ERRα circuit and consequent oxidative phosphorylation, O2 consumption, and ATP production. This circuit may play an important role in repairing neurovascular function after TBI in the peri-injured region by stimulating astrocytic mitochondrial biogenesis.

Korean red ginseng alleviate depressive disorder by improving astrocyte gap junction function.

ETHNOPHARMACOLOGICAL RELEVANCE: Korean red ginseng (KRG), a processed product of Panax ginseng C. A. Mey, show significant anti-depressive effect in clinic. However, its mechanism is still unclear. AIM OF THE STUDY: Gap junction intercellular communication (GJIC) dysfunction is a potential pathogenesis of depression. Therefore, this study's objective is to investigate whether the antidepressant effect of KRG is related to GJIC. MATERIALS AND METHODS: Rat were restraint 8 h every day for 28 consecutive days to prepare depression models, and meanwhile, rats were intragastrically administrated with normal saline, KRG solutions (25, 50 or 100 mg/kg) or fluoxetine (10 mg/kg) 1 h before stress. The behavioral performance was determined by forced swimming test, sucrose preference test and open field test. GJIC was determined by the Lucifer yellow (LY) diffusion distance in prelimb cortex (PLC). In addition, the level of Cx43, one of executors of GJIC, was tested by Western blot. To find out the protective effect of KRG against GJIC dysfunction directly, rats were intracranially injected with carbenoxolone (CBX, blocker of GJIC), and meanwhile normal saline, KRG (100 mg/kg) or fluoxetine (10 mg/kg) was administered daily. The behavioral performance of these rats was detected, and the LY localization injection PLC area was used to detect the gap junction function. RESULTS: Chronic resistant stress (CRS) induced depressive symptoms, as manifested by prolonged immobility time in forced swimming test and decreased sucrose consumption ratio. Administration of KRG alleviated these depressive symptoms significantly. GJIC determination showed that KRG improved the LY diffusion and increased Cx43 level in prefrontal cortex (PFC) significantly, indicated that GJIC dysfunction was alleviated by the treatment of KRG. However, the astrocytes number was also increased by the treatment of KRG, which maybe alleviate depression-like symptoms by increasing the number of astrocytes rather than improving GJIC. Injection of CBX produced depressive symptoms and GJIC dysfunction, as manifested by decreased sucrose consumption ratio and prolonged immobility time in forced swimming test, but no astrocytes number changes, KRG also reversed depressive symptoms and GJIC dysfunction, suggested that the improvement of depressive-like symptoms was improved by GJIC. CONCLUSIONS: KRG alleviate depressive disorder by improving astrocytic gap junction function.

Dynamic Transitions of Epilepsy Waveforms Induced by Astrocyte Dysfunction and Electrical Stimulation.

Experimental studies have shown that astrocytes participate in epilepsy through inducing the release of glutamate. Meanwhile, considering the disinhibition circuit among inhibitory neuronal populations with different time scales and the feedforward inhibition connection from thalamic relay nucleus to cortical inhibitory neuronal population, here, we propose a modified thalamocortical field model to systematically investigate the mechanism of epilepsy. Firstly, our results show that rich firing activities can be induced by astrocyte dysfunction, including high or low saturated state, high- or low-frequency clonic, spike-wave discharge (SWD), and tonic. More importantly, with the enhancement of feedforward inhibition connection, SWD and tonic oscillations will disappear. In other words, all these pathological waveforms can be suppressed or eliminated. Then, we explore the control effects after different external stimulations applying to thalamic neuronal population. We find that single-pulse stimulation can not only suppress but also induce pathological firing patterns, such as SWD, tonic, and clonic oscillations. And we further verify that deep brain stimulation can control absence epilepsy by regulating the amplitude and pulse width of stimulation. In addition, based on our modified model, 3 : 2 coordinated reset stimulation strategies with different intensities are compared and a more effective and safer stimulation mode is proposed. Our conclusions are expected to give more theoretical insights into the treatment of epilepsy.

Dietary quercetin attenuates depressive-like behaviors by inhibiting astrocyte reactivation in response to stress.

The mechanisms underlying the antidepressant activity of quercetin are unknown. We investigated the effect of a quercetin-enriched diet (2 g/kg and 0.5 g/kg doses) on chronic social defeat stress (CSDS)-induced depressive-like behaviors in mice. The 2 g/kg quercetin-enriched diet attenuated depressive-like behaviors when introduced before CSDS (long-term). The long-term 0.5 g/kg quercetin-enriched diet showed a trend toward behavioral improvement. The frequencies of spontaneous excitatory postsynaptic currents (sEPSCs) and spontaneous inhibitory postsynaptic currents (sIPSCs) in the mPFC and hippocampus were significantly higher in mice fed the long-term 2 g/kg quercetin-enriched diet compared with the normal diet; no difference was found in the amygdala. Quercetin-enriched diets administered concurrently and after stress induction failed to trigger these effects. A1-specific astrocyte reactivity was markedly suppressed in the microglia and astrocytes isolated from the mPFC and hippocampus of mice fed the long-term quercetin-enriched diet, but not in those who received quercetin supplementation concurrently or after CSDS. To confirm the role of astrocytes in the neuroprotective effect of quercetin, we activated astrocytes by injecting a chemogenic AAV stimulus into the mPFC and hippocampus and found that astrocyte activation during administration of the long-term quercetin-enriched diet significantly deceased the frequency of sEPSCs and sIPSCs in the mPFC and hippocampus and further attenuated quercetin-induced behavioral improvements. These findings highlight the key role of astrocyte reactivation in the regulation of quercetin neuroprotective activity and suggest that a diet high in quercetin, whether as a fruit- and vegetable-rich diet or food additive may help cope with stress.

Astrocytes Control Sensory Acuity via Tonic Inhibition in the Thalamus.

Sensory discrimination is essential for survival. However, how sensory information is finely controlled in the brain is not well defined. Here, we show that astrocytes control tactile acuity via tonic inhibition in the thalamus. Mechanistically, diamine oxidase (DAO) and the subsequent aldehyde dehydrogenase 1a1 (Aldh1a1) convert putrescine into GABA, which is released via Best1. The GABA from astrocytes inhibits synaptically evoked firing at the lemniscal synapses to fine-tune the dynamic range of the stimulation-response relationship, the precision of spike timing, and tactile discrimination. Our findings reveal a novel role of astrocytes in the control of sensory acuity through tonic GABA release.

Hypothalamic Astrocyte Development and Physiology for Neuroprogesterone Induction of the Luteinizing Hormone Surge.

Neural circuits in female rats sequentially exposed to estradiol and progesterone underlie so-called estrogen positive feedback that induce the surge release of pituitary luteinizing hormone (LH) leading to ovulation and luteinization of the corpus hemorrhagicum. It is now well-established that gonadotropin releasing hormone (GnRH) neurons express neither the reproductively critical estrogen receptor-α (ERα) nor classical progesterone receptor (PGR). Estradiol from developing ovarian follicles acts on ERα-expressing kisspeptin neurons in the rostral periventricular region of the third ventricle (RP3V) to induce PGR expression, and kisspeptin release. Circulating estradiol levels that induce positive feedback also induce neuroprogesterone (neuroP) synthesis in hypothalamic astrocytes. This local neuroP acts on kisspeptin neurons that express PGR to augment kisspeptin expression and release needed to stimulate GnRH release, triggering the LH surge. In vitro and in vivo studies demonstrate that neuroP signaling in kisspeptin neurons occurs through membrane PGR activation of Src family kinase (Src). This signaling cascade has been also implicated in PGR signaling in the arcuate nucleus of the hypothalamus, suggesting that Src may be a common mode of membrane PGR signaling. Sexual maturation requires that signaling between neuroP synthesizing astrocytes, kisspeptin and GnRH neurons be established. Prior to puberty, estradiol does not facilitate the synthesis of neuroP in hypothalamic astrocytes. During pubertal development, levels of membrane ERα increase in astrocytes coincident with an increase of PKA phosphorylation needed for neuroP synthesis. Currently, it is not clear whether these developmental changes occur in existing astrocytes or are due to a new population of astrocytes born during puberty. However, strong evidence suggests that it is the former. Blocking new cell addition during puberty attenuates the LH surge. Together these results demonstrate the importance of pubertal maturation involving hypothalamic astrocytes, estradiol-induced neuroP synthesis and membrane-initiated progesterone signaling for the CNS control of ovulation and reproduction.

Mapping astrocyte activity domains by light sheet imaging and spatio-temporal correlation screening.

Astrocytes are a major type of glial cell in the mammalian brain, essentially regulating neuronal development and function. Quantitative imaging represents an important approach to study astrocytic signaling in neural circuits. Focusing on astrocytic Ca2+ activity, a key pathway implicated in astrocye-neuron interaction, we here report a strategy combining fast light sheet fluorescence microscopy (LSFM) and correlative screening-based time series analysis, to map activity domains in astrocytes in living mammalian nerve tissue. Light sheet of micron-scale thickness enables wide-field optical sectioning to image astrocytes in acute mouse brain slices. Using both chemical and genetically encoded Ca2+ indicators, we demonstrate the complementary advantages of LSFM in mapping Ca2+ domains in astrocyte populations as compared to epifluorescence and two-photon microscopy. Our approach then revealed distinct kinetics of Ca2+ signals between cortical and hypothalamic astrocytes in resting conditions and following the activation of adrenergic G protein coupled receptor (GPCR). This observation highlights the activity heterogeneity across regionally distinct astrocyte populations, and indicates the potential of our method for investigating dynamic signals in astrocytes.

The Contribution of Astrocyte Autophagy to Systemic Metabolism.

Autophagy is an essential mechanism to maintain cellular homeostasis. Besides its role in controlling the quality of cytoplasmic components, it participates in nutrient obtaining and lipid mobilization under stressful conditions. Furthermore, autophagy is involved in the regulation of systemic metabolism as its blockade in hypothalamic neurons can affect the central regulation of metabolism and impact body energy balance. Moreover, hypothalamic autophagy can be altered during obesity, one of the main alterations of metabolism nowadays. In this review, we focus on the role of astrocytes, essential cells for brain homeostasis, which represent key metabolic regulators. Astrocytes can sense metabolic signals in the hypothalamus and modulate systemic functions as glucose homeostasis and feeding response. Moreover, the response of astrocytes to obesity has been widely studied. Astrocytes are important mediators of brain inflammation and can be affected by increased levels of saturated fatty acids associated with obesity. Although autophagy plays important roles for astrocyte homeostasis and functioning, the contribution of astrocyte autophagy to systemic metabolism has not been analyzed yet. Furthermore, how obesity can impact astrocyte autophagy is poorly understood. More studies are needed in order to understand the contribution of astrocyte autophagy to metabolism.

Prevention of systemic inflammation and neuroprotective effects of Qingda granules against angiotensin II-mediated hypertension.

Qingxuan Jiangya Decoction (QXJYD), prescribed by academician Ke-ji Chen, has long been used as a Traditional Chinese Medicine formula in blood pressure control and has achieved good clinical outcomes in hypertensive patients. Qingda granules (QDGs), which is a formula simplified from QXJYD, might serve as a novel anti-hypertensive pharmaceutical. However, the functional mechanism of QDGs remains unclear. This study aimed to evaluate the effect of QDGs against the elevation of blood pressure, systemic inflammation and brain injury in Ang II-mediated hypertensive mice. Ang II-mediated hypertensive mice were treated with 28.63mg QDG of per mouse every day. The blood pressure of all mice was measured on days 0, 1, 3, 5, 7, 14 and 28 by using the tail-cuff plethysmograph method. Following 28 days of treatment, the mice were sacrificed and their whole blood and brain tissues were used for analysis. The results showed that QDGs significantly decreased elevated systolic and diastolic blood pressure in Ang II-mediated hypertensive mice while body weight did not change, which demonstrated anti-hypertensive activities of QDGs without obvious toxicity. QDGs significantly attenuated the level of serum cytokines (IL-6, TNF-a) and chemokines (MCP-1, MIP-1a, RANTES) in the Ang II-mediated hypertensive mice. Moreover, pathological staining showed that QDGs significantly ameliorated cerebral histopathology changes, reduced the loss of neurons and activations of astrocytes. Additionally, QDGs inhibited neuronal apoptosis by down-regulation of Bax expression and up-regulation of Bcl-2 expression. These results suggested that QDGs exhibited excellent anti-hypertensive properties by preventing systemic inflammation and providing neuroprotective effects against Ang II-mediated hypertension.

Astroglial changes in the zona incerta in response to motor cortex stimulation in a rat model of chronic neuropathy.

Although astrocytes are known to regulate synaptic transmission and affect new memory formation by influencing long-term potentiation and functional synaptic plasticity, their role in pain modulation is poorly understood. Motor cortex stimulation (MCS) has been used to reduce neuropathic pain through the incertothalamic pathway, including the primary motor cortex (M1) and the zona incerta (ZI). However, there has been no in-depth study of these modulatory effects and region-specific changes in neural plasticity. In this study, we investigated the effects of MCS-induced pain modulation as well as the relationship between the ZI neuroplasticity and MCS-induced pain alleviation in neuropathic pain (NP). MCS-induced threshold changes were evaluated after daily MCS. Then, the morphological changes of glial cells were compared by tissue staining. In order to quantify the neuroplasticity, MAP2, PSD95, and synapsin in the ZI and M1 were measured and analyzed with western blot. In behavioral test, repetitive MCS reduced NP in nerve-injured rats. We also observed recovered GFAP expression in the NP with MCS rats. In the NP with sham MCS rats, increased CD68 level was observed. In the NP with MCS group, increased mGluR1 expression was observed. Analysis of synaptogenesis-related molecules in the M1 and ZI revealed that synaptic changes occured in the M1, and increased astrocytes in the ZI were more closely associated with pain alleviation after MCS. Our findings suggest that MCS may modulate the astrocyte activities in the ZI and synaptic changes in the M1. Our results may provide new insight into the important and numerous roles of astrocytes in the formation and function.

Spatiotemporal model of tripartite synapse with perinodal astrocytic process.

Information transfer may not be limited only to synapses. Therefore, the processes and dynamics of biological neuron-astrocyte coupling and intercellular interaction within this domain are worth investigating. Existing models of tripartite synapse consider an astrocyte as a point process. Here, we extended the tripartite synapse model by considering the astrocytic processes (synaptic and perinodal) as compartments. The scattered extrinsic signals in the extracellular space and the presence of calcium stores in different astrocytic sites create local transient [Ca2+]. We investigated the Ca2+ dynamics and found that the increase in astrocytic intracellular [Ca2+] enhances the probability of neurotransmitter release. However, the period in which the extrasynaptic glutamate lingers in the extracellular space may cause excitotoxicity. We propose further biological investigation on intercellular communication, considering that unconventional sources (nonsynaptic) of glutamate may improve information processing in neuron-astrocyte networks.

The Stabilization of Central Sympathetic Nerve Activation by Renal Denervation Prevents Cerebral Vasospasm after Subarachnoid Hemorrhage in Rats.

The poor prognosis of subarachnoid hemorrhage (SAH) might be associated with sympathetic nerve activation (catecholamine surge) initiated by hypothalamic injury. As renal denervation (RD) has been shown to exert protective effects on cardiovascular dysfunction by suppressing increased central sympathetic nerve activation, we examined whether RD improved the experimental SAH prognosis in this study. Two hundred thirty-eight male Sprague-Dawley rats were divided into sham-operated and SAH-operated groups, and then each rat was further separated into Sham-operated and RD-operated groups. Bilateral RD was performed approximately 45 min after SAH induction. We examined the effect of RD on early brain injury (EBI) and delayed cerebral ischemia (DCI) as a primary endpoint, and also explored the effect on cerebral vasospasm (CVS) as a secondary endpoint. Although RD did not exert significant effects on primary endpoint, RD significantly prevented CVS and reduced SAH-induced increases in the number of phosphorylated extracellular signal-regulated kinase (ERK)-positive endothelial cells, cyclooxygenase-2 expression, and macrophage infiltration in major cerebral arteries. Moreover, RD significantly decreased the areas displaying dopamine ß-hydroxylase and glial fibrillary acidic protein immunopositivity in the paraventricular nucleus of the hypothalamus and serum angiotensin II levels, all of which were increased by SAH. Although RD decreased systolic blood pressure, significant changes in cerebral blood flow were not observed compared with SAH + Sham group. Based on the findings, RD improved CVS by reducing endothelial cell damage and the effects were associated with the stabilization of central sympathetic nerve activation in a SAH model.

What Do Microglia Really Do in Healthy Adult Brain?

Microglia originate from yolk sac-primitive macrophages and auto-proliferate into adulthood without replacement by bone marrow-derived circulating cells. In inflammation, stroke, aging, or infection, microglia have been shown to contribute to brain pathology in both deleterious and beneficial ways, which have been studied extensively. However, less is known about their role in the healthy adult brain. Astrocytes and oligodendrocytes are widely accepted to strongly contribute to the maintenance of brain homeostasis and to modulate neuronal function. On the other hand, contribution of microglia to cognition and behavior is only beginning to be understood. The ability to probe their function has become possible using microglial depletion assays and conditional mutants. Studies have shown that the absence of microglia results in cognitive and learning deficits in rodents during development, but this effect is less pronounced in adults. However, evidence suggests that microglia play a role in cognition and learning in adulthood and, at a cellular level, may modulate adult neurogenesis. This review presents the case for repositioning microglia as key contributors to the maintenance of homeostasis and cognitive processes in the healthy adult brain, in addition to their classical role as sentinels coordinating the neuroinflammatory response to tissue damage and disease.

Time to Target Stroke: Examining the Circadian System in Stroke.

Stroke is the 5th leading cause of death in the United States and a leading cause of long-term disability. Ischemic strokes account for 87 percent of total stroke cases, yet the only FDA-approved treatments involve disruption of the blood clot to restore blood flow. New treatments aimed at saving or protecting neural tissue have largely failed in clinical trials and so new methodology or targets must be found. The occurrence of strokes significantly increases between 6 AM and 12 PM, implicating the circadian system in the onset of this debilitating brain injury. But it is not known whether or how the circadian system may regulate the response to and recovery from stroke. New strategies to identify treatments for stroke are beginning to look at cell types other than neurons as therapeutic targets, including astrocytes. In this review, we present links between the astrocyte circadian clock, the molecular response to stroke, and the damage caused by ischemia. We highlight aspects of astrocyte circadian function that could dictate new methodologies for stroke treatment, including the potential of chronotherapy.

Human iPSC-Derived Blood-Brain Barrier Chips Enable Disease Modeling and Personalized Medicine Applications.

The blood-brain barrier (BBB) tightly regulates the entry of solutes from blood into the brain and is disrupted in several neurological diseases. Using Organ-Chip technology, we created an entirely human BBB-Chip with induced pluripotent stem cell (iPSC)-derived brain microvascular endothelial-like cells (iBMECs), astrocytes, and neurons. The iBMECs formed a tight monolayer that expressed markers specific to brain vasculature. The BBB-Chip exhibited physiologically relevant transendothelial electrical resistance and accurately predicted blood-to-brain permeability of pharmacologics. Upon perfusing the vascular lumen with whole blood, the microengineered capillary wall protected neural cells from plasma-induced toxicity. Patient-derived iPSCs from individuals with neurological diseases predicted disease-specific lack of transporters and disruption of barrier integrity. By combining Organ-Chip technology and human iPSC-derived tissue, we have created a neurovascular unit that recapitulates complex BBB functions, provides a platform for modeling inheritable neurological disorders, and advances drug screening, as well as personalized medicine.

Molecular mechanisms of microglia- and astrocyte-driven neurorestoration triggered by application of electromagnetic fields.

AIM: To propose potential mechanisms of action of electromagnetic fields (EMF) on astrocytes and microglia and to elucidate the role of heat shock proteins (HSP), adenosine triphosphate (ATP), calcium ions (Ca2+), and hypoxia-inducible factor 1α (HIF1α) in neurorestoration following the application of EMF. METHODS: We reviewed the existing studies within the public domain and cross-evaluated their results in order to conclude on the molecular mechanisms of microglia-astrocyte crosstalk at work during EMF treatment. RESULTS: The existing studies suggest that EMF induces the increase of HSP70 expression and inhibition of HIF1α, thus decreasing inflammation and allowing the microglia-astrocyte crosstalk to initiate the formation of a glial scar within the central nervous system. Furthermore, by potentially up-regulating A2A and A3 adenosine receptors, EMF increases cAMP accumulation from astrocytes and reduces the expression of inflammatory cytokines TNF α and IL-8, thus initiating neurorestoration. CONCLUSION: The microglia-astrocyte crosstalk during EMF treatment is crucial for the initiation of neurorestoration. Elucidating the exact mechanisms of EMF actions upon microglia and astrocytes, and its role in neurorestoration could be a key step in further research of the therapeutic potential of EMFs in various neurological disorders.

Effects of cyclic AMP on the differentiation and bioenergetics of rat C6 glioma cells.

INTRODUCTION: Elevation in the level of intracellular cAMP is known to induce astrocytic differentiation of C6 glioma cells by unknown mechanisms. METHODS: Therefore, cytoskeletal protein genes (phalloidin) fluorescents to investigate morphological changes, cell proliferation assay, MTT assay, flow cytometry, western blotting, in-cell western, immune-cytochemical (protein expression and localization), and oxygen electrodes (oxygen consumption rate) after a treatment with 0.25 mM dbcAMP were conducted. RESULTS: Undifferentiated cells (media without dbcAMP) showed a flat polygonal appearance, whereas those cultured in the presence of 0.25 mM dbcAMP exhibited a more differentiated astrocytic morphology. They had more numerous neurite-like thin processes. The cell proliferation of differentiated c6 glioma reduced at day 2 and then started to increase at day 3 till day 5 compared to undifferentiated c6 glioma cells. In terms of flow-cytometry data, dbcAMP had no apoptotic effect on the C6 glioma cells. There was an increase in the protein expression GFAP (specific marker for astrocytes). There was no significant effect between undifferentiated and 5-day differentiation regarding their response to glucose 10 mM. In addition, there were no significant effects of glucose on the basal of 5-day differentiation of C6 glioma cells. However, there was a significant correlation between the concentration of glucose and inhibition of the basal oxygen consumption. Finally, glucose 10 mM did not stimulate NAD (P)H levels of C6 glioma cells. CONCLUSION: The above results showed that cAMP induce C6 glioma cells differentiation without affecting its bioenergetics. Therefore cAMP is considered to be the best differentiating agent.

Glial Regulation of Energy Metabolism.

The major function of brain glial cells is to maintain a homeostatic milieu for neurons to work properly in response to a variety of environmental alterations. Recent studies have shown that glial cells in the hypothalamus, a brain center controlling homeostatic physiological functions, are essential for regulating energy metabolism in both physiological and pathological conditions. Astrocytes, tanycytes, and NG2-glia shuttle and/or sense key metabolic factors presented to the hypothalamus either directly, by glial metabolic enzymes, receptors, and transporters, or indirectly, by modulating the sensing ability of other types of hypothalamic cells. Astrocytes, tanycytes, and microglia are critically important in the development and maintenance of hypothalamic circuits regulating energy balance. Hypothalamic inflammation commonly associated with diet-induced obesity is manifested via hypothalamic reactive gliosis involving microglia and astrocytes, contributing to the correlated abnormal energy metabolism. Although many glial functions in energy metabolism remain to be fully elucidated, we are at the dawn of targeting glia-neuron interactions in the hypothalamus for therapeutic applications in metabolic disorders.