Potential role of hippocampal neurogenesis in spinal cord injury induced post-trauma depression

It has been reported both in clinic and rodent models that beyond spinal cord injury directly induced symptoms, such as paralysis, neuropathic pain, bladder/bowel dysfunction, and loss of sexual function, there are a variety of secondary complications, including memory loss, cognitive decline, depression, and Alzheimer's disease. The largescale longitudinal population-based studies indicate that post-trauma depression is highly prevalent in spinal cord injury patients. Yet, few basic studies have been conducted to address the potential molecular mechanisms. One of possible factors underlying the depression is the reduction of adult hippocampal neurogenesis which may come from less physical activity, social isolation, chronic pain, and elevated neuroinflammation after spinal cord injury. However, there is no clear consensus yet. In this review, we will first summarize the alteration of hippocampal neurogenesis post-spinal cord injury. Then, we will discuss possible mechanisms underlie this important spinal cord injury consequence. Finally, we will outline the potential therapeutic options aimed at enhancing hippocampal neurogenesis to ameliorate depression.

Changes in structural plasticity of hippocampal neurons in an animal model of multiple sclerosis

Structural plasticity is critical for the functional diversity of neurons in the brain.Experimental autoimmune encephalomyelitis(EAE)is the most commonly used model for multiple sclerosis(MS),successfully mimicking its key pathological features(inflammation,demyelination,axonal loss,and gliosis)and clinical symptoms(motor and non-motordysfunctions).Recentstudieshave demonstrated the importance of synaptic plasticity in EAE pathogenesis.In the present study,we investigated the features of behavioral alteration and hippocampal structural plasticity in EAE-affected mice in the early phase(11 days post-immunization,DPI)and chronic phase(28DPI).EAE-affected mice exhibited hippocampus-related behavioral dysfunction in the open field test during both early and chronic phases.Dendritic complexity was largely affected in the cornu ammonis 1(CA1)and CA3 apical and dentate gyrus(DG)subregions of the hippocampus during the chronic phase,while this effect was only noted in the CA1 apical subregion in the early phase.Moreover,dendritic spine density was reduced in the hippocampal CA1 and CA3 apical/basal and DG subregions in the early phase of EAE,but only reduced in the DG subregion during the chronic phase.Furthermore,mRNA levels of proinflammatory cytokines(Il1β,Tnfα,and Ifnγ)and glial cell markers(Gfap and Cd68)were significantly increased,whereas the expression of activity-regulated cytoskeletonassociated protein(ARC)was reduced during the chronic phase.Similarly,exposure to the aforementioned cytokines in primary cultures of hippocampal neurons reduced dendritic complexity and ARC expression.Primary cultures of hippocampal neurons also showed significantly reduced extracellular signal-regulated kinase(ERK)phosphorylation upon treatment with proinflammatory cytokines.Collectively,these results suggest that autoimmune neuroinflammation alters structural plasticity in the hippocampus,possibly through the ERK-ARC pathway,indicating that this alteration may be associated with hippocampal dysfunctions in EAE.

Inverse relationship between platelet Akt activity and hippocampal atrophy:A pilot case-control study in patients with diabetes mellitus

BACKGROUND Akt plays diverse roles in humans.It is involved in the pathogenesis of type 2 diabetes mellitus(T2DM),which is caused by insulin resistance.Akt also plays a vital role in human platelet activation.Furthermore,the hippocampus is closely associated with memory and learning,and a decrease in hippocampal volume is reportedly associated with an insulin-resistant phenotype in T2DM patients without dementia.AIM To investigate the relationship between Akt phosphorylation in unstimulated platelets and the hippocampal volume in T2DM patients.METHODS Platelet-rich plasma(PRP)was prepared from the venous blood of patients with T2DM or age-matched controls.The pellet lysate of the centrifuged PRP was subjected to western blotting to analyse the phosphorylation of Akt,p38 mitogen-activated protein(MAP)kinase and glyceraldehyde 3-phosphate dehydrogenase(GAPDH).Phosphorylation levels were quantified by densitometric analysis.Hippocampal volume was analysed using a voxel-based specific regional analysis system for Alzheimer’s disease on magnetic resonance imaging,which proposes the Z-score as a parameter that reflects hippocampal volume.RESULTS The levels of phosphorylated Akt corrected with phosphorylated p38 MAP kinase were inversely correlated with the Z-scores in the T2DM subjects,whereas the levels of phosphorylated Akt corrected with GAPDH were not.However,this relationship was not observed in the control patients.CONCLUSION These results suggest that an inverse relationship may exist between platelet Akt activation and hippocampal atrophy in T2DM patients.Our findings provide insight into the molecular mechanisms underlying T2DM hippocampal atrophy.

Melatonin:a multitasking indoleamine to modulate hippocampal neurogenesis

Neurodegeneration affects a large number of cell types including neurons,astrocytes or oligodendrocytes,and neural stem cells.Neural stem cells can generate new neuronal populations through proliferation,migration,and differentiation.This neurogenic potential may be a relevant factor to fight neurodegeneration and aging.In the last years,we can find growing evidence suggesting that melatonin may be a potential modulator of adult hippocampal neurogenesis.The lack of therapeutic strategies targeting neurogenesis led researchers to explore new molecules.Numerous preclinical studies with melatonin observed how melatonin can modulate and enhance molecular and signaling pathways involved in neurogenesis.We made a special focus on the connection between these modulation mechanisms and their implication in neurodegeneration,to summarize the current knowledge and highlight the therapeutic potential of melatonin.

Mitochondrial transplantation ameliorates hippocampal damage following status epilepticus

Background:Hippocampal damage caused by status epilepticus(SE)can bring about cognitive decline and emotional disorders,which are common clinical comorbidities in patients with epilepsy.It is therefore imperative to develop a novel therapeutic strat-egy for protecting hippocampal damage after SE.Mitochondrial dysfunction is one of contributing factors in epilepsy.Given the therapeutic benefits of mitochondrial replenishment by exogenous mitochondria,we hypothesized that transplantation of mitochondria would be capable of ameliorating hippocampal damage following SE.Methods:Pilocarpine was used to induced SE in mice.SE-generated cognitive de-cline and emotional disorders were determined using novel object recognition,the tail suspension test,and the open field test.SE-induced hippocampal pathology was assessed by quantifying loss of neurons and activation of microglia and astrocytes.The metabolites underlying mitochondrial transplantation were determined using metabonomics.Results:The results showed that peripheral administration of isolated mitochon-dria could improve cognitive deficits and depressive and anxiety-like behaviors.Exogenous mitochondria blunted the production of reactive oxygen species,pro-liferation of microglia and astrocytes,and loss of neurons in the hippocampus.The metabonomic profiles showed that mitochondrial transplantation altered multiple metabolic pathways such as sphingolipid signaling pathway and carbon metabolism.Among potential affected metabolites,mitochondrial transplantation decreased levels of sphingolipid(d18:1/18:0)and methylmalonic acid,and elevated levels of D-fructose-1,6-bisphosphate.Conclusion:To the best of our knowledge,these findings provide the first direct ex-perimental evidence that artificial mitochondrial transplantation is capable of amelio-rating hippocampal damage following SE.These new findings support mitochondrial transplantation as a promising therapeutic strategy for epilepsy-associated psychiat-ric and cognitive disorders.

Electroacupuncture alleviates orofacial allodynia and anxiety-like behaviors by regulating synaptic plasticity of the CA1 hippocampal region in a mouse model of trigeminal neuralgia

OBJECTIVE To investigate whether electroacupuncture(EA)ameliorates abnormal trigeminal neuralgia(TN)orofacial pain and anxiety-like behavior by altering synaptic plasticity in the hippocampus CA1.METHODS A mouse infraorbital nerve transection model(pTION)of neuropathic pain was established,and EA or sham EA was used to treat ipsilateral acu⁃puncture points(GV20-Baihui and ST7-Xia⁃guan).Golgi-Cox staining and transmission elec⁃tron microscopy(TEM)were administrated to observe the changes of synaptic plasticity in the hippocampus CA1.RESULTS Stable and persistent orofacial allodynia and anxiety-like behav⁃iors induced by pT-ION were related to changes in hippocampal synaptic plasticity.Golgi stain⁃ings showed a decrease in the density of dendritic spines,especially mushroom-type dendritic spines,in hippocampal CA1 neurons of pT-ION mice.TEM results showed that the density of synapses,membrane thickness of the postsynaptic density,and length of the synaptic active zone were decreased,whereas the width of the synaptic cleft was increased in pTION mice.EA attenu⁃ated pT-ION-induced orofacial allodynia and anx⁃iety-like behaviors and effectively reversed the abnormal changes in dendritic spines and syn⁃apse of the hippocampal CA1 region.CONCLU⁃SION EA modulates synaptic plasticity of hippo⁃campal CA1 neurons,and reduces abnormal oro⁃facial pain and anxiety-like behavior,providing evidence for a TN treatment strategy.

Formation of the entorhino-hippocampal pathway: a tracing study in vitro and in vivo

Objective The entorhino-hippocampal pathway is the major excitatory input from neurons of the entorhinal cortex on both ipsilateral and contralateral hippocampus/dentate gyrus. This fiber tract consists of the alvear path, the perforant path and a crossed commissural projection. In this study, the histogenesis and development of the various subsets of the entorhino-hippocampal projection have been investigated. Methods Dil, DiO and fast blue tracing as well as anti-calretinin immunocytochemistry were carried out with prenatal and postnatal rats at different ages. Results The alvear path and the commissural pathway started to develop as early as embryonic day （E） 16, while the first perforant afferents reached the stratum lacunosum-moleculare of the hippocampus at E 17 and the outer molecular layer of dentate gyrus at postnatal day （P） 2, respectively. Retrograde tracing with DiI identified entorhinal neurons in layer II to IV as the origin of entorhino-hippocampal pathway. Furthermore, anti-calretinin immunocytochemistry revealed transitory Cajal- Retzius （CR） cells in the stratum lacunosum-moleculare of the hippocampus from as early as E 16. DiI labeling of entorhinal cortex fibers and combined calretinin-immunocytochemistry showed a close association between CR cells and entorhinal afferents. Conclusion The subsets of entorhino-hippocampal pathway appear in the developmental hippocampus during El6 - P2. The temporal and spatial relationship between CR cell and perforant afferent suggests the role of this cell type as a guiding cue for entorhinal afferents at early cortical development.

Adult hippocampal neurogenesis and its impairment in Alzheimer's disease

Adult neurogenesis is the creation of new neurons which integrate into the existing neural circuit of the adult brain.Recent evidence suggests that adult hippocampal neurogenesis(AHN)persists throughout life in mammals,including humans.These newborn neurons have been implicated to have a crucial role in brain functions such as learning and memory.Importantly,studies have also found that hippocampal neurogenesis is impaired in neurodegenerative and neuropsychiatric diseases.Alzheimer’s disease(AD)is one of the most common forms of dementia affecting millions of people.Cognitive dysfunction is a common symptom of AD patients and progressive memory loss has been attributed to the degeneration of the hippocampus.Therefore,there has been growing interest in identifying how hippocampal neurogenesis is affected in AD.However,the link between cognitive decline and changes in hippocampal neurogenesis in AD is poorly understood.In this review,we summarized the recent literature on AHN and its impairments in AD.

Effect of acetylcholine on pain-related electric activities in hippocampal CA1 area of normal and morphinistic rats

Objective To examine the effect of acetylcholine（ACh）on the electric activities of pain-excitation neurons （PEN）and pain-inhibitation neurons（PIN）in the hippocampal CA1 area of normal rats or morphinistic rats,and to explore the role of ACh in regulation of pain perception in CA1 area under normal condition and morphine addiction.Methods The trains of electric impulses applied to sciatic nerve were set as noxious stimulation.The discharges of PEN and PIN in the CA l area were recorded extracellularly by glass microelectrode.We observed the influence of intracerebroventricular （i.c.v.）injection of ACh and atropine on the noxious stimulation-evoked activities of PEN and PIN in the CA1 area.Results Noxious stimulation enhanced the electric activity of PEN and depressed that of PIN in the CA1 area of both normal and addiction rats.In normal rats,ACh decrease the pain-evoked discharge frequency of PEN,while increased the frequency of PIN.These effects reached the peak value at 4 min after injection of ACh.In morphinistic rats,ACh also inhibited the PEN electric activity and potentialized the PIN electric activity,but the maximum effect appeared at 6 min after administration. The ACh-induced responses were significantly blocked by muscarinic receptor antagonist atropine.Conclusion Cholinergic neurons and muscarinic receptors in the hippocampal CA1 area are involved in the processing of nociceptive information and they may play an analgesia role in pain modulation.Morphine addiction attenuated the sensitivity of painrelated neurons to the noxious information.

Neuroprotective effects of ginsenoside Rb1 on hippocampal neuronal injury and neurite outgrowth

Ginsenoside Rb1 has been reported to exert anti-aging and anti-neurodegenerative effects. In the present study, we investigate whether ginsenoside Rb1 is involved in neurite outgrowth and neuroprotection against damage induced by amyloid beta（25–35） in cultured hippocampal neurons, and explore the underlying mechanisms. Ginsenoside Rb1 significantly increased neurite outgrowth in hippocampal neurons, and increased the expression of phosphorylated-Akt and phosphorylated extracellular signal-regulated kinase 1/2. These effects were abrogated by API-2 and PD98059, inhibitors of the signaling proteins Akt and MEK. Additionally, cultured hippocampal neurons were exposed to amyloid beta（25–35） for 30 minutes; ginsenoside Rb1 prevented apoptosis induced by amyloid beta（25–35）, and this effect was blocked by API-2 and PD98059. Furthermore, ginsenoside Rb1 significantly reversed the reduction in phosphorylated-Akt and phosphorylated extracellular signal-regulated kinase 1/2 levels induced by amyloid beta（25–35）, and API-2 neutralized the effect of ginsenoside Rb1. The present results indicate that ginsenoside Rb1 enhances neurite outgrowth and protects against neurotoxicity induced by amyloid beta（25–35） via a mechanism involving Akt and extracellular signal-regulated kinase 1/2 signaling.

Role of chloride channels in nitric oxide-induced rat hippocampal neuronal apoptosis in vitro

BACKGROUND：Chloride channels participate in non-neuronal apoptosis.However,it remains unclear whether chloride channels are involved in ischemic neuronal apoptosis.OBJECTIVE：To explore the effects of 4-acetamido-4＇-isothiocyanatostilbene-2,2＇-disulfonic acid （SITS） and 4,4＇-diisothiocyanostilbene-2,2＇-disulfonic acid （DIDS）,two chloride channel blockers,on the hippocampal neuronal apoptosis induced by 3-morpholinosydnonimine （SIN-1） based on the nitric oxide toxicity theory of neuronal apoptosis following ischemic brain injury.DESIGN,TIME AND SETTING：Comparative observation and in vitro experiments were performed at the laboratory of Zhuhai Campus of Zunyi Medical College from January to May 2009.MATERIALS：SIN-1,SITS,and DIDS were purchased from Sigma,USA.METHODS：Hippocampal neurons from Sprague-Dawley rats,aged 1 day,were cultured In vitro for 12 days and randomly assigned to control,SIN-1,or chloride channel blocker groups.SIN-1 group neurons were induced by SIN-1 for 18 hours to establish a model of ischemic neuronal apoptosis.Neurons in chloride channel blocker groups were treated with SITS or DIDS plus SIN-1 for 18 hours.The controls were cultured in DMEM/Ham＇s F12 complete medium alone.MAIN OUTCOME MEASURES：The apoptotic neurons and nuclear appearance were detected by Hoechst 33258 fluorescence staining; neuronal viability was quantitatively determined by 3-（4,5-dimethylthiazol-2-yl）-2,5-diphenyltetrazolium bromide analysis.Caspase-3 activity was analyzed by Western blot.RESULTS：SIN-1 （1 mmol/L） dramatically induced apoptosis （50%-60%）.SITS and DIDS inhibited nitric oxide-induced neuronal injury in a dose-dependent manner,suppressed caspase-3 activation,reduced neuronal apoptosis,and improved neuronal survival.CONCLUSION：Chloride channel blockers can protect against neuronal injury induced by NO.Chloride channels might be involved in neuronal apoptosis following cerebral ischemia.

Ginsenoside Rg1 protects against neurodegeneration by inducing neurite outgrowth in cultured hippocampal neurons

Ginsenoside Rg1（Rg1） has anti-aging and anti-neurodegenerative effects. However, the mechanisms underlying these actions remain unclear. The aim of the present study was to determine whether Rg1 affects hippocampal survival and neurite outgrowth in vitro after exposure to amyloid-beta peptide fragment 25–35（Aβ_（25–35））, and to explore whether the extracellular signal-regulated kinase（ERK） and Akt signaling pathways are involved in these biological processes. We cultured hippocampal neurons from newborn rats for 24 hours, then added Rg1 to the medium for another 24 hours, with or without pharmacological inhibitors of the mitogen-activated protein kinase（MAPK） family or Akt signaling pathways for a further 24 hours. We then immunostained the neurons for growth associated protein-43, and measured neurite length. In a separate experiment, we exposed cultured hippocampal neurons to Aβ_（25–35） for 30 minutes, before adding Rg1 for 48 hours, with or without Akt or MAPK inhibitors, and assessed neuronal survival using Hoechst 33258 staining, and phosphorylation of ERK1/2 and Akt by western blot analysis. Rg1 induced neurite outgrowth, and this effect was blocked by API-2（Akt inhibitor） and PD98059（MAPK/ERK kinase inhibitor）, but not by SP600125 or SB203580（inhibitors of c-Jun N-terminal kinase and p38 MAPK, respectively）. Consistent with this effect, Rg1 upregulated the phosphorylation of Akt and ERK1/2; these effects were reversed by API-2 and PD98059, respectively. In addition, Rg1 significantly reversed Aβ_（25–35）-induced apoptosis; this effect was blocked by API-2 and PD98059, but not by SP600125 or SB203580. Finally, Rg1 significantly reversed the Aβ_（25–35）-induced decrease in Akt and ERK1/2 phosphorylation, but API-2 prevented this reversal. Our results indicate that Rg1 enhances neurite outgrowth and protects against Aβ_（25–35）-induced damage, and that its mechanism may involve the activation of Akt and ERK1/2 signaling.

Protective mechanisms of micro RNA-27a against oxygen-glucose deprivation-induced injuries in hippocampal neurons

Hypoxic injuries during fetal distress have been shown to cause reduced expression of micro RNA-27a（mi R-27a）,which regulates sensitivity of cortical neurons to apoptosis.We hypothesized that miR-27 a overexpression attenuates hypoxia- and ischemia-induced neuronal apoptosis by regulating FOXO1,an important transcription factor for regulating the oxidative stress response.miR-27 a mimic was transfected into hippocampal neurons to overexpress miR-27 a.Results showed increased hippocampal neuronal viability and decreased caspase-3 expression.The luciferase reporter gene system demonstrated that mi R-27 a directly binded to FOXO1 3′UTR in hippocampal neurons and inhibited FOXO1 expression,suggesting that FOXO1 was the target gene for mi R-27 a.These findings confirm that mi R-27 a protects hippocampal neurons against oxygen-glucose deprivation-induced injuries.The mechanism might be mediated by modulation of FOXO1 and apoptosis-related gene caspase-3 expression.

Characterization of astrocytes and microglial cells in the hippocampal CA1 region after transient focal cerebral ischemia in rats treated with Ilexonin A

Ilexonin A is a compound isolated from the root of Ilex pubescens,a traditional Chinese medicine.Ilexonin A has been shown to play a neuroprotective role by regulating the activation of astrocytes and microglia in the peri-infarct area after ischemia.However,the effects of ilexonin A on astrocytes and microglia in the infarct-free region of the hippocampal CA1 region remain unclear.Focal cerebral ischemia models were established by 2-hour occlusion of the middle cerebral artery in rats.Ilexonin A(20,40 or 80 mg/kg)was administered immediately after ischemia/reperfusion.The astrocyte marker glial fibrillary acidic protein,microglia marker Iba-1,neural stem cell marker nestin and inflammation markers were detected by immunohistochemistry and western blot assay.Expression levels of tumor necrosis factor-αand interleukin 1βwere determined by enzyme linked immunosorbent assay in the hippocampal CA1 tissue.Astrocytes were activated immediately in progressively increasing numbers from 1,3,to 7 days post-ischemia/reperfusion.The number of activated astrocytes further increased in the hippocampal CA1 region after treatment with ilexonin A.Microglial cells remained quiescent after ischemia/reperfusion,but became activated after treatment with ilexonin A.Ilexonin A enhanced nestin expression and reduced the expression of tumor necrosis factor-αand interleukin 1βin the hippocampus post-ischemia/reperfusion.The results of the present study suggest that ilexonin A has a neuroprotective effect in the hippocampus after ischemia/reperfusion,probably through regulating astrocytes and microglia activation,promoting neuronal stem cell proliferation and reducing the levels of pro-inflammatory factors.This study was approved by the Animal Ethics Committee of the Fujian Medical University Union Hospital,China.

N-methyl-D-aspartate receptor subunit 1 regulates neurogenesis in the hippocampal dentate gyrus of schizophrenia-like mice

N-methyl-D-aspartate receptor hypofunction is the basis of pathophysiology in schizophrenia. Blocking the N-methyl-D-aspartate receptor impairs learning and memory abilities and induces pathological changes in the brain. Previous studies have paid little attention to the role of the N-methyl-D-aspartate receptor subunit 1 (NR1) in neurogenesis in the hippocampus of schizophrenia. A mouse model of schizophrenia was established by intraperitoneal injection of 0.6 mg/kg MK-801, once a day, for 14 days. In N-methyl-D-aspartate-treated mice, N-methyl-D-aspartate was administered by intracerebroventricular injection in schizophrenia mice on day 15. The number of NR1-, Ki67- or BrdU-immunoreactive cells in the dentate gyrus was measured by immunofluorescence staining. Our data showed the number of NR1-immunoreactive cells increased along with the decreasing numbers of BrdU- and Ki67-immunoreactive cells in the schizophrenia groups compared with the control group. N-methyl-D-aspartate could reverse the above changes. These results indicated that NR1 can regulate neurogenesis in the hippocampal dentate gyrus of schizophrenia mice, supporting NR1 as a promising therapeutic target in the treatment of schizophrenia. This study was approved by the Experimental Animal Ethics Committee of the Ningxia Medical University, China (approval No. 2014-014) on March 6, 2014.

Exploration of the mechanism by which icariin modulates hippocampal neurogenesis in a rat model of depression

Icariin(ICA) has a significant capacity to protect against depression and hippocampal injury,but it cannot effectively cross the bloodbrain barrier and accumulate in the brain.Therefore,the mechanism by which ICA protects against hippocampal injury in depression remains unclear.In this study,we performed proteomics analysis of cerebrospinal fluid to investigate the mechanism by which ICA prevents dysfunctional hippocampal neurogenesis in depression.A rat model of depression was established through exposure to chronic unpredictable mild stress for 6 weeks,after which 120 mg/kg ICA was administered subcutaneously every day.The results showed that ICA alleviated depressive symptoms,learning and memory dysfunction,dysfunctional neurogenesis,and neuronal loss in the dentate gyrus of rats with depression.Neural stem cells from rat embryonic hippocampi were cultured in media containing 20% cerebrospinal fluid from each group of rats and then treated with 100 μM corticosterone.The addition of cerebrospinal fluid from rats treated with ICA largely prevented the corticosterone-mediated inhibition of neuronal proliferation and differentiation.Fifty-two differentially expressed proteins regulated by chronic unpredictable mild stress and ICA were identified through proteomics analysis of cerebrospinal fluid.These proteins were mainly involved in the ribosome,PI3 K-Akt signaling,and interleukin-17 signaling pathways.Parallel reaction monitoring mass spectrometry showed that Rps4 x,Rps12,Rps14,Rps19,Hsp90 b1,and Hsp90 aa1 were up-regulated by chronic unpredictable mild stress and down-regulated by ICA.In contrast,Htr A1 was down-regulated by chronic unpredictable mild stress and up-regulated by ICA.These findings suggest that ICA can prevent depression and dysfunctional hippocampal neurogenesis through regulating the expression of certain proteins found in the cerebrospinal fluid.The study was approved by the Experimental Animal Ethics Committee of Guangzhou University of Chinese Medicine of China in March 2017.

Real-time Microwave Exposure Induces Calcium Efflux in Primary Hippocampal Neurons and Primary Cardiomyocytes

Objective To detect the effects of microwave on calcium levels in primary hippocampal neurons and primary cardiomyocytes by the real-time microwave exposure combined with laser scanning confocal microscopy. Methods The primary hippocampal neurons and primary cardiomyocytes were cultured and labeled with probes, including Fluo-4 AM, Mag-Fluo-AM, and Rhod-2, to reflect the levels of whole calcium [Ca], endoplasmic reticulum calcium [Ca]ER, and mitochondrial calcium [Ca]MIT, respectively. Then, the cells were exposed to a pulsed microwave of 2.856 GHz with specific absorption rate(SAR) values of 0, 4, and 40 W/kg for 6 min to observe the changes in calcium levels. Results The results showed that the 4 and 40 W/kg microwave radiation caused a significant decrease in the levels of [Ca], [Ca]ER, and [Ca]MIT in primary hippocampal neurons. In the primary cardiomyocytes, only the 40 W/kg microwave radiation caused the decrease in the levels of [Ca], [Ca]ER, and [Ca]MIT. Primary hippocampal neurons were more sensitive to microwave exposure than primary cardiomyocytes. The mitochondria were more sensitive to microwave exposure than the endoplasmic reticulum. Conclusion The calcium efflux was occurred during microwave exposure in primary hippocampal neurons and primary cardiomyocytes. Additionally, neurons and mitochondria were sensitive cells and organelle respectively.

Exendin-4 attenuates pain-induced cognitive impairment by alleviating hippocampal neuroinflammation in a rat model of spinal nerve ligation

Glucagon-like peptide-1 receptor has anti-apoptotic,anti-inflammatory,and neuroprotective effects.It is now recognized that the occurrence and development of chronic pain are strongly associated with anti-inflammatory responses;however,it is not clear whether glucagon-like peptide-1 receptor regulates chronic pain via anti-inflammatory mechanisms.We explored the effects of glucagon-like peptide-1 receptor on nociception,cognition,and neuroinflammation in chronic pain.A rat model of chronic pain was established using left L5 spinal nerve ligation.The glucagon-like peptide-1 receptor agonist exendin-4 was intrathecally injected into rats from 10 to 21 days after spinal nerve ligation.Electrophysiological examinations showed that,after treatment with exendin-4,paw withdrawal frequency of the left limb was significantly reduced,and pain was relieved.In addition,in the Morris water maze test,escape latency increased and the time to reach the platform decreased following exendin-4 treatment.Immunohistochemical staining and western blot assays revealed an increase in the numbers of activated microglia and astrocytes in the dentate gyrus of rat hippocampus,as well as an increase in the expression of tumor necrosis factor alpha,interleukin 1 beta,and interleukin 6.All of these effects could be reversed by exendin-4 treatment.These findings suggest that exendin-4 can alleviate pain-induced neuroinflammatory responses and promote the recovery of cognitive function via the glucagon-like peptide-1 receptor pathway.All experimental procedures and protocols were approved by the Experimental Animal Ethics Committee of Renmin Hospital of Wuhan University of China(approval No.WDRM 20171214)on September 22,2017.

Chrysophanol attenuates lead exposure-induced injury to hippocampal neurons in neonatal mice

Previous studies have shown that chrysophanol protects against learning and memory impairments in lead-exposed adult mice. In the present study, we investigated whether chrysophanol can alleviate learning and memory dysfunction and hippocampal neuronal injury in lead-exposed neonatal mice. At the end of lactation, chrysophanol（0.1, 1.0, 10.0 mg/kg） was administered to the neonatal mice by intraperitoneal injection for 15 days. Chrysophanol significantly alleviated injury to hippocampal neurons and improved learning and memory abilities in the lead-poisoned neonatal mice. Chrysophanol also significantly decreased lead content in blood, brain, heart, spleen, liver and kidney in the lead-exposed neonatal mice. The levels of malondialdehyde in the brain, liver and kidney were significantly reduced, and superoxide dismutase and glutathione peroxidase activities were significantly increased after chrysophanol treatment. Collectively, these findings indicate that chrysophanol can significantly reduce damage to hippocampal neurons in lead-exposed neonatal mice.

Astragalus injection inhibits c-Jun N terminal kinase mRNA expression following oxygen-glucose deprivation and reintroduction in rat hippocampal neurons

BACKGROUND： In studies concerning cell injury induced by cerebral ischemia-reperfusion, current experiments have primarily focused on altered protein levels. In addition, the apoptotic proteins Bax and Bcl-2 have been thoroughly studied with regard to initiating neuronal apoptosis. OBJECTIVE： To establish an in vitro model of oxygen-glucose deprivation and reintroduction in the rat hippocampus to simulate cerebral ischemia-reperfusion injury; to observe c-Jun N-terminal kinase 3 （JNK3） mRNA expression in hippocampal neurons following Astragalus injection; and thus to determine changes in the signaling and downstream pathways of neuronal apoptosis at the cellular and molecular level. DESIGN, TIME AND SETTING： A randomized, controlled, cellular and molecular experiment was performed at the Department of Central Laboratory, Chengde Medical College from February to June 2008. MATERIALS： Astragalus injection, the main ingredient of astragaloside, was purchased from Chengdu Di＇ao Jiuhong Pharmaceutical Manufactory, China. JNK3 mRNA probe and in situ hybridization kit were purchased from Tianjin Haoyang Biological Technology, China, and JNK3 RT-PCR primers were designed by Shanghai Bio-engineering, China. METHODS： Primary cultures of hippocampal neurons derived from Sprague Dawley rats, aged 1 2 days, were established. After 8 days, the hippocampal neurons were assigned to the following interventions： model group, Astragalus group, and vehicle control group, cells were subjected to oxygen-glucose reintroduction after oxygen-glucose deprivation for 30 minutes in sugar-free Earle＇s solution and a hypoxia device, which contained high-purity nitrogen. The normal control group was subjected to primary culture techniques and was not treated using above-mentioned interventions. In addition, the Astragalus and vehicle control groups were treated with Astragalus injection （0.5 g/L raw drug） or sterile, deionized water at 2 hours prior to oxygen-glucose deprivation, respectively. MAIN OUTCOME MEASURES： JNK3 mRNA expression was measured by in situ hybridization and RT-PCR at 0, 0.5, 2, 6, 24, 72, and 120 hours after oxygen-glucose reintroduction. RESULTS： Hippocampal neuronal morphology was normal in the normal control group. Hippocampal neurons exhibited apparent apoptosis-like pathological changes in the model, as well as the vehicle control, groups. The apoptosis-like pathological changes in the hippocampal neurons were less in the Astragalus group. Results from in situ hybridization and RT-PCR showed that JNK3 mRNA expression significantly increased in hippocampal neurons from model group, as well as the vehicle control group, compared with the normal control group （P 〈 0.05）. In addition, JNK3 mRNA expression significantly decreased in hippocampal neurons of the Astragalus group, compared with the model group and vehicle control group （P 〈 0.05）. CONCLUSION： Astragalus injection inhibited apoptosis-related JNK3 mRNA expression following oxygen-glucose deprivation and reintroduction, and accordingly played a role in inhibiting hippocampal neuronal apoptosis.