Survival Of Hippocampal Neurons Research Articles

Honokiol relieves hippocampal neuronal damage in Alzheimer's disease by activating the SIRT3-mediated mitochondrial autophagy.

This work elucidated the effect of honokiol (HKL) on hippocampal neuronal mitochondrial function in Alzheimer's disease (AD). APP/PS1 mice were used as AD mice models and exposed to HKL and 3-TYP. Morris water maze experiment was performed to appraise cognitive performance of mice. Hippocampal Aβ+ plaque deposition and neuronal survival was evaluated by immunohistochemistry and Nissl staining. Hippocampal neurons were dissociated from C57BL/6 mouse embryos. Hippocampal neuronal AD model was constructed by Aβ oligomers induction and treated with HKL, CsA and 3-TYP. Neuronal viability and apoptosis were detected by cell counting kit-8 assay and TUNEL staining. mRFP-eGFP-LC3 assay, MitoSOX Red, dichlorodihydrofluorescein diacetate, and JC-1 staining were performed to monitor neuronal autophagosomes, mitochondrial reactive oxygen species (ROS), neuronal ROS, and mitochondrial membrane potential. Autophagy-related proteins were detected by Western blot. In AD mice, HKL improved cognitive function, relieved hippocampal Aβ1-42 plaque deposition, promoted hippocampal neuron survival, and activated hippocampal SIRT3 expression and mitochondrial autophagy. These effects of HKL on AD mice were abolished by 3-TYP treatment. In hippocampal neuronal AD model, HKL increased neuronal activity, attenuated neuronal apoptosis and Aβ aggregation, activated SIRT3 and mitochondrial autophagy, reduced mitochondrial and neuronal ROS, and elevated mitochondrial membrane potential. CsA treatment and 3-TYP treatment abrogated the protection of HKL on hippocampal neuronal AD model. The promotion of mitochondrial autophagy by HKL in hippocampal neuronal AD model was counteracted by 3-TYP. HKL activates SIRT3-mediated mitochondrial autophagy to mitigate hippocampal neuronal damage in AD. HKL may be effective in treating AD.

Environmental enrichment and the combined interventions of EE and metformin enhance hippocampal neuron survival and hippocampal-dependent memory in type 2 diabetic rats under stress through the BDNF-TrkB signaling pathways

BackgroundType 2 diabetes (T2D) with depression causes severe cognitive impairments. The devastating conditions will further compromise the overall quality of life. The overconsumption of high-fat and high-sucrose (HFS) diet is one of the modifiable risk factors for T2D, depression, and cognitive impairments. Thus, it is essential to identify effective therapeutic strategies to overcome the cognitive impairments in T2D with depression. We proposed environmental enrichment (EE) which encompasses social, cognitive, and physical components as the alternative treatment for such impairments. We also investigated the potential neuroprotective properties of the antidiabetic drug metformin. This study aimed to investigate the effects of EE and metformin interventions on hippocampal neuronal death, and hippocampal-dependent memory impairment in T2D rats under stress. MethodsThirty-two male rats (200–250 g) were divided into four groups: C group (standard diet + conventional cage), DS group [HFS-induced T2D + restraint stress (RS)], DSE group [HFS-induced T2D + RS + EE] and DSEM group [HFS + RS + EE + metformin]. Serum corticosterone (CORT) was measured to evaluate stress levels. The serum Free Oxygen Radicals Testing (FORT) and Free Oxygen Radicals Defence Test (FORD) were measured to evaluate the systemic oxidative status (OS). Serum brain-derived neurotrophic factor (BDNF) and T-maze tasks were performed to evaluate cognitive functions. Rats were humanely sacrificed to collect brains for histological, morphometric, and hippocampal gene expression studies. ResultsThe CORT and the serum FORT levels in the DSE and DSEM groups were lower than in the DS group. Meanwhile, the serum BDNF, T-maze scores, histological, and morphometric analysis were improved in the DSE and DSEM groups than in the DS group. These findings supported that EE and the combined interventions of EE and metformin had neuroprotective properties. The hippocampal gene expression analysis revealed that the DSE and DSEM groups showed improved regulation of BDNF-TrkB signalling pathways, including the BDNF/TrkB binding, PI3K – Akt pathway, Ras–MAPK pathway, PLCγ–Ca2+ pathway, and CREB transcription. ConclusionEE and the combined interventions of EE and metformin improved hippocampal neuron survival and hippocampal-dependent memory in T2D rats under stress by enhancing gene expression regulation of neurogenesis and synaptic plasticity.

Retraction: Regulation of extracellular signal-regulated kinase 1/2 influences hippocampal neuronal survival in a rat model of diabetic cerebral ischemia.

Retraction: Regulation of extracellular signal-regulated kinase 1/2 influences hippocampal neuronal survival in a rat model of diabetic cerebral ischemia.

Effects of Gestational Exercise on Nociception, BDNF, and Irisin Levels in an Animal Model of ADHD

Abnormal cognitive and sensorial properties have been reported in patients with psychiatric and neurodevelopmental conditions, such as attention deficit hyperactivity disorder (ADHD). ADHD patients exhibit impaired dopaminergic signaling and plasticity in brain areas related to cognitive and sensory processing. The spontaneous hypertensive rat (SHR), in comparison to the Wistar Kyoto rat (WKY), is the most used genetic animal model to study ADHD. Brain neurotrophic factor (BDNF), critical for midbrain and hippocampal dopaminergic neuron survival and differentiation, is reduced in both ADHD subjects and SHR. Physical exercise (e.g. swimming) promotes neuroplasticity and improves cognition by increasing BDNF and irisin. Here we investigate the effects of gestational swimming on sensorial and behavioral phenotypes, striatal dopaminergic parameters, and hippocampal FNDC5/irisin and BDNF levels observed in WKY and SHR. Gestational swimming improved nociception in SHR rats (p = 0.006) and increased hippocampal BDNF levels (p = 0.02) in a sex-dependent manner in adolescent offspring. Sex differences were observed in hippocampal FNDC5/irisin levels (p = 0.002), with females presenting lower levels than males. Our results contribute to the notion that swimming during pregnancy is a promising alternative to improve ADHD phenotypes in the offspring.

Role of an interdependent Wnt, GSK3-β/β-catenin and HB-EGF/EGFR mechanism in arsenic-induced hippocampal neurotoxicity in adult mice

We previously reported the neurotoxic effects of arsenic in the hippocampus. Here, we explored the involvement of Wnt pathway, which contributes to neuronal functions. Administering environmentally relevant arsenic concentrations to postnatal day-60 (PND60) mice demonstrated a dose-dependent increase in hippocampal Wnt3a and its components, Frizzled, phospho-LRP6, Dishevelled and Axin1 at PND90 and PND120. However, p-GSK3-β(Ser9) and β-catenin levels although elevated at PND90, decreased at PND120. Additionally, treatment with Wnt-inhibitor, rDkk1, reduced p-GSK3-β(Ser9) and β-catenin at PND90, but failed to affect their levels at PND120, indicating a time-dependent link with Wnt. To explore other underlying factors, we assessed epidermal growth factor receptor (EGFR) pathway, which interacts with GSK3-β and appears relevant to neuronal functions. We primarily found that arsenic reduced hippocampal phosphorylated-EGFR and its ligand, Heparin-binding EGF-like growth factor (HB-EGF), at both PND90 and PND120. Moreover, treatment with HB-EGF rescued p-GSK3-β(Ser9) and β-catenin levels at PND120, suggesting their HB-EGF/EGFR-dependent regulation at this time point. Additionally, rDkk1, LiCl (GSK3-β-activity inhibitor), or β-catenin protein treatments induced a time-dependent recovery in HB-EGF, indicating potential inter-dependent mechanism between hippocampal Wnt/β-catenin and HB-EGF/EGFR following arsenic exposure. Fluorescence immunolabeling then validated these findings in hippocampal neurons. Further exploration of hippocampal neuronal survival and apoptosis demonstrated that treatment with rDkk1, LiCl, β-catenin and HB-EGF improved Nissl staining and NeuN levels, and reduced cleaved-caspase-3 levels in arsenic-treated mice. Supportively, we detected improved Y-Maze and Passive Avoidance performances for learning-memory functions in these mice. Overall, our study provides novel insights into Wnt/β-catenin and HB-EGF/EGFR pathway interaction in arsenic-induced hippocampal neurotoxicity.

Slc20a1 and Slc20a2 regulate neuronal plasticity and cognition independently of their phosphate transport ability

In recent years, primary familial brain calcification (PFBC), a rare neurological disease characterized by a wide spectrum of cognitive disorders, has been associated to mutations in the sodium (Na)-Phosphate (Pi) co-transporter SLC20A2. However, the functional roles of the Na-Pi co-transporters in the brain remain still largely elusive. Here we show that Slc20a1 (PiT-1) and Slc20a2 (PiT-2) are the most abundant Na-Pi co-transporters expressed in the brain and are involved in the control of hippocampal-dependent learning and memory. We reveal that Slc20a1 and Slc20a2 are differentially distributed in the hippocampus and associated with independent gene clusters, suggesting that they influence cognition by different mechanisms. Accordingly, using a combination of molecular, electrophysiological and behavioral analyses, we show that while PiT-2 favors hippocampal neuronal branching and survival, PiT-1 promotes synaptic plasticity. The latter relies on a likely Otoferlin-dependent regulation of synaptic vesicle trafficking, which impacts the GABAergic system. These results provide the first demonstration that Na-Pi co-transporters play key albeit distinct roles in the hippocampus pertaining to the control of neuronal plasticity and cognition. These findings could provide the foundation for the development of novel effective therapies for PFBC and cognitive disorders.

BDNF-TrkB/proBDNF-p75NTR pathway regulation by lipid emulsion rescues bupivacaine-induced central neurotoxicity in rats

Bupivacaine (BPV) can cause severe central nervous system toxicity when absorbed into the blood circulation system. Rapid intravenous administration of lipid emulsion (LE) could be used to treat local anaesthetic toxicity. This study aimed to investigate the mechanism by which the BDNF-TrkB/proBDNF-p75NTR pathway regulation by LE rescues BPV induced neurotoxicity in hippocampal neurons in rats. Seven- to nine-day-old primary cultured hippocampal neurons were randomly divided into 6 groups: the blank control group (Ctrl), the bupivacaine group (BPV), the lipid emulsion group (LE), the bupivacaine + lipid emulsion group (BPV + LE), the bupivacaine + lipid emulsion + tyrosine kinase receptor B (TrkB) inhibitor group (BPV + LE + K252a), the bupivacaine + lipid emulsion + p75 neurotrophic factor receptor (p75NTR) inhibitor group (BPV + LE + TAT-Pep5). All hippocampal neurons were incubated for 24 h, and their growth state was observed by light microscopy. The relative TrkB and p75NTR mRNA levels were detected by real-time PCR. The protein expression levels of brain-derived neurotrophic factor (BDNF), proBDNF, TrkB, p75NTR and cleaved caspase-3 were detected by western blotting. The results showed that primary hippocampal neuron activity was reduced by BPV. As administration of LE elevated hippocampal neuronal activity, morphology was also somewhat improved. The protein expression and mRNA levels of TrkB and p75NTR were decreased when BPV induced hippocampal neuronal toxicity, while the expression of BDNF was increased. At the same time, BPV increased the original generation of cleaved caspase-3 protein content by hippocampal neurons, while the content of cleaved caspase-3 protein in hippocampal neurons cotreated with LE and BPV was decreased. Thus, this study has revealed LE may reduce apoptosis and promote survival of hippocampal neurons by regulating the BDNF-TrkB pathway and the proBDNF-p75NTR pathway to rescue BPV induced central neurotoxicity in rats.

Expression and role of cocaine-amphetamine regulated transcript (CART) in the proliferation of biliary epithelium.

Cholangiocytes, the epithelial cells that line the biliary tree, can proliferate under the stimulation of several factors through both autocrine and paracrine pathways. The cocaine-amphetamine-regulated-transcript (CART) peptide has several physiological functions, and it is widely expressed in several organs. CART increases the survival of hippocampal neurons by upregulating brain-derived neurotrophic factor (BDNF), whose expression has been correlated to the proliferation rate of cholangiocytes. In the present study, we aimed to evaluate the expression of CART and its role in modulating cholangiocyte proliferation in healthy and bile duct ligated (BDL) rats in vivo, as well as in cultured normal rat cholangiocytes (NRC) in vitro. Liver samples from both healthy and BDL (1 week) rats, were analyzed by immunohistochemistry and immunofluorescence for CART, CK19, TrkB and p75NTR BDNF receptors. PCNA staining was used to evaluate the proliferation of the cholangiocytes, whereas TUNEL assay was used to evaluate biliary apoptosis. NRC treated or not with CART were used to confirm the role of CART on cholangiocytes proliferation and the secretion of BDNF. Cholangiocytes proliferation, apoptosis, CART and TrkB expression were increased in BDL rats, compared to control rats. We found a higher expression of TrkB and p75NTR, which could be correlated with the proliferation rate of biliary tree during BDL. The in vitro study demonstrated increased BDNF secretion by NRC after treatment with CART compared with control cells. As previously reported, proliferating cholangiocytes acquire a neuroendocrine phenotype, modulated by several factors, including neurotrophins. Accordingly, CART may play a key role in the remodeling of biliary epithelium during cholestasis by modulating the secretion of BDNF.

Dexmedetomidine alleviates cognitive impairment by promoting hippocampal neurogenesis via BDNF/TrkB/CREB signaling pathway in hypoxic-ischemic neonatal rats.

Dexmedetomidine (DEX) has been reported to alleviate hypoxic-ischemic brain damage (HIBD) in neonates. This study aimed to investigate whether DEX improves cognitive impairment by promoting hippocampal neurogenesis via the BDNF/TrkB/CREB signaling pathway in neonatal rats with HIBD. HIBD was induced in postnatal day 7 rats using the Rice-Vannucci method, and DEX (25 μg/kg) was administered intraperitoneally immediately after the HIBD induction. The BDNF/TrkB/CREB pathway was regulated by administering the TrkB receptor antagonist ANA-12 through intraperitoneal injection or by delivering adeno-associated virus (AAV)-shRNA-BDNF via intrahippocampal injection. Western blot was performed to measure the levels of BDNF, TrkB, and CREB. Immunofluorescence staining was utilized to identify the polarization of astrocytes and evaluate the levels of neurogenesis in the dentate gyrus of the hippocampus. Nissl and TTC staining were performed to evaluate the extent of neuronal damage. The MWM test was conducted to evaluate spatial learning and memory ability. The levels of BDNF and neurogenesis exhibited a notable decrease in the hippocampus of neonatal rats after HIBD, as determined by RNA-sequencing technology. Our results demonstrated that treatment with DEX effectively increased the protein expression of BDNF and the phosphorylation of TrkB and CREB, promoting neurogenesis in the dentate gyrus of the hippocampus in neonatal rats with HIBD. Specifically, DEX treatment significantly augmented the expression of BDNF in hippocampal astrocytes, while decreasing the proportion of detrimental A1 astrocytes and increasing the proportion of beneficial A2 astrocytes in neonatal rats with HIBD. Furthermore, inhibiting the BDNF/TrkB/CREB pathway using either ANA-12 or AAV-shRNA-BDNF significantly counteracted the advantageous outcomes of DEX on hippocampal neurogenesis, neuronal survival, and cognitive improvement. DEX promoted neurogenesis in the hippocampus by activating the BDNF/TrkB/CREB pathway through the induction of polarization of A1 astrocytes toward A2 astrocytes, subsequently mitigating neuronal damage and cognitive impairment in neonates with HIBD.

Voluntary Running Improves Behavioral and Structural Abnormalities in a Mouse Model of CDKL5 Deficiency Disorder.

Cyclin-dependent kinase-like 5 (CDKL5) deficiency disorder (CDD) is a rare neurodevelopmental disease caused by mutations in the X-linked CDKL5 gene. CDD is characterized by a broad spectrum of clinical manifestations, including early-onset refractory epileptic seizures, intellectual disability, hypotonia, visual disturbances, and autism-like features. The Cdkl5 knockout (KO) mouse recapitulates several features of CDD, including autistic-like behavior, impaired learning and memory, and motor stereotypies. These behavioral alterations are accompanied by diminished neuronal maturation and survival, reduced dendritic branching and spine maturation, and marked microglia activation. There is currently no cure or effective treatment to ameliorate the symptoms of the disease. Aerobic exercise is known to exert multiple beneficial effects in the brain, not only by increasing neurogenesis, but also by improving motor and cognitive tasks. To date, no studies have analyzed the effect of physical exercise on the phenotype of a CDD mouse model. In view of the positive effects of voluntary running on the brain of mouse models of various human neurodevelopmental disorders, we sought to determine whether voluntary daily running, sustained over a month, could improve brain development and behavioral defects in Cdkl5 KO mice. Our study showed that long-term voluntary running improved the hyperlocomotion and impulsivity behaviors and memory performance of Cdkl5 KO mice. This is correlated with increased hippocampal neurogenesis, neuronal survival, spine maturation, and inhibition of microglia activation. These behavioral and structural improvements were associated with increased BDNF levels. Given the positive effects of BDNF on brain development and function, the present findings support the positive benefits of exercise as an adjuvant therapy for CDD.

Gastrodin ameliorates cognitive dysfunction in diabetes by inhibiting PAK2 phosphorylation.

Diabetes is associated with higher prevalence of cognitive dysfunction, while the underlying mechanism is still elusive. In this study, we aim to explore the potential mechanism of diabetes-induced cognitive dysfunction and assess the therapeutic effects of Gastrodin on cognitive dysfunction. Diabetes was induced by a single injection of streptozotocin. The Morris Water Maze Test was employed to assess the functions of spatial learning and memory. Transcriptome was used to identify the potential factors involved. Western blot and immunofluorescence were applied to detect the protein expression. Our results have shown that spatial learning was impaired in diabetic rats, coupled with damaged hippocampal pyramidal neurons. Gastrodin intervention ameliorated the spatial learning impairments and neuronal damages. Transcriptomics analysis identified differential expression genes critical for diabetes-induced hippocampal damage and Gastrodin treatment, which were further confirmed by qPCR and western blot. Moreover, p21 activated kinase 2 (PAK2) was found to be important for diabetes-induced hippocampal injury and its inhibitor could promote the survival of primary hippocampal neurons. It suggested that PAK2 pathway may be involved in cognitive dysfunction in diabetes and could be a therapeutic target for Gastrodin intervention.

Sub-dose anesthetics combined with chloride regulators protect the brain against chronic ischemia-hypoxia injury.

Cerebral ischemia-hypoxia leads to excitotoxicity-mediated neuronal damage and cognitive dysfunction, especially in the elderly. Excessive intracellular [Cl- ]i accumulation weakens γ-aminobutyric acid (GABA) compensatory effects. Sub-anesthetic dose of propofol protected the brain against ischemia-hypoxia, which was abolished by blocking Cl- efflux transporter K+ /Cl- cotransporter 2 (KCC2). We aimed to determine whether low-dose anesthetic combined with [Cl- ]i regulators could restore the compensatory GABAergic system and improve cognitive function. Chronic cerebral hypoxia (CCH) model was established by bilateral carotid artery ligation in aged rats. Sub-dose of anesthetics (propofol and sevoflurane) with or without KCC2 agonist N-ethylmaleimide (NEM) or Na+ /K+ /Cl- cotransporter 1 (NKCC1) antagonist bumetanide (BTN) was administered systemically 30 days post-surgery. Primary rat hippocampal neuronal cultures were subjected to hypoxic injury with or without drug treatment. Memory function, hippocampal neuronal survival, GABAergic system functioning, and brain-derived neurotrophic factor (BDNF) expressions were evaluated. Sub-anesthetic dose of combined propofol (1.2 μg mL-1 ) and sevoflurane [0.7 MAC (minimum alveolar concentration)] did not aggravate the hypoxic brain injury in rats or cell damage in neuronal cultures. Adding either BTN or NEM protected against hypoxic injury, associated with improved cognitive function in vivo, less intracellular accumulation of [Cl- ]i , reduced cell death, restored GABAergic compensation, and increased BDNF expression both in vivo and in vitro. Sub-anesthetic dose of propofol and sevoflurane is a recommended anesthesia regimen in at-risk patients. Restoration of [Cl- ]i homeostasis and GABAergic could further reduce the brain damage caused by ischemia-hypoxia.

MiR-34a targets SIRT1 to reduce p53 deacetylation and promote sevoflurane inhalation anesthesia-induced neuronal autophagy and apoptosis in neonatal mice

This study is to investigate the function of miR-34a and interactions between miR-34a, SIRT1, and p53 in sevoflurane-induced neuronal apoptosis and autophagy in neonatal mice. A mouse model was established by inhalation anesthesia with sevoflurane and injected with genetic reagents, followed by tests of learning and memory abilities and histological staining of the hippocampus. CCK-8 and AnnexinV/PI staining respectively measured the survival and apoptosis rates of primary hippocampal neurons cultured with sevoflurane. The expression levels of miR-34a, SIRT1, p53, Ac-p53, and autophagy- or apoptosis-related proteins were measured. Sevoflurane impaired the learning and memory abilities of mice, increased TUNEL-positive cells in their hippocampus, and hindered the survival of hippocampal neurons. Sevoflurane increased miR-34a, Bax, cleaved caspase-3, and the ratio of LC3-II/LC3-I and reduced SIRT1 and p62. MiR-34a overexpression promoted sevoflurane-induced neural damage, whereas SIRT1 inhibition or p53 upregulation counteracted the neuroprotection of miR-34a knockdown. SIRT1 was a target of miR-34a and promoted p53 deacetylation. MiR-34a promotes sevoflurane-stimulated neuronal apoptosis and autophagy in neonatal mice by inhibiting SIRT1 expression and subsequent p53 deacetylation.

Abelmoschus esculentus (Okra) Prevents Insulin Resistance and Restores Neuron Autophagy by Regulating Dipeptidyl Peptidase-4 and Thus Improving Hippocampal Function.

Diabetes is highly linked to the occurrence of Alzheimer disease (AD), which is characterized by beta amyloid peptide (Aβ) and hyperphosphorylation of tau (p-tau), and neuron damage particularly in hippocampus. Type 2 diabetes (T2D) is featured by insulin resistance, and phosphorylation of Ser307-IRS-1 is regarded as a resistance marker. Inhibitors of dipeptidyl peptidase-4 (DPP-4) are effective tools for treating T2D. Previously, we reported subfractions of Abelmoschus esculentus (AE, okra) (F1 rich in quercetin glycosides; F2 composed of polysaccharide) attenuated DPP-4 and its downstream signals of insulin resistance, thus preventing Aβ-induced neuron damage. Since autophagy could be protective, we now explore if AE works to modulate neuron autophagy by regulating DPP-4 and insulin resistance and, thus, improves the hippocampal function and behavior. We demonstrated that AE subfractions attenuate Aβ-induced insulin resistance and the expression of p-tau and normalize the autophagy and survival of hippocampal neurons. The action of AE may be attributed to the downregulation of DPP-4, which plays a critical role in mediating insulin resistance and hinders neuron autophagy. The in vivo findings reveal that the hippocampal insulin resistance appears to link with loss of memory, reduction of curiosity, and depression, whereas treatment with AE significantly improves the insulin sensitivity and hippocampal function. Noteworthy, even at only 5 μg/mL, F2 seems to exhibit a meaningful effect. In conclusion, we suggest that AE attenuates insulin resistance and recovers neuron autophagy which are regulated by DPP-4, thus preventing the damage to the hippocampus, improving recognition and emotion. AE may be an effective adjuvant or supplement to prevent insulin resistance-associated pathogenesis of AD if these results can be confirmed in human clinical trials.

Aminoprocalcitonin protects against hippocampal neuronal death via preserving oxidative phosphorylation in refractory status epilepticus

Refractory status epilepticus (RSE) is a neurological emergency where sustaining seizure causes severe neuronal death. Currently, there is no available neuroprotectant effective in RSE. Aminoprocalcitonin (NPCT) is a conserved peptide cleaved from procalcitonin, but its distribution and function in the brain remain enigmatic. Survival of neurons relies on sufficient energy supply. Recently, we found that NPCT was extensively distributed in the brain and had potent modulations on neuronal oxidative phosphorylation (OXPHOS), suggesting that NPCT might be involved in neuronal death by regulating energy status. In the present study, combining biochemical and histological methods, high-throughput RNA-sequence, Seahorse XFe analyser, an array of mitochondria function assays, and behavior-electroencephalogram (EEG) monitoring, we investigated the roles and translational values of NPCT in neuronal death after RSE. We found that NPCT was extensively distributed throughout gray matters in rat brain while RSE triggered NPCT overexpression in hippocampal CA3 pyramidal neurons. High-throughput RNA-sequence demonstrated that the influences of NPCT on primary hippocampal neurons were enriched in OXPHOS. Further function assays verified that NPCT facilitated ATP production, enhanced the activities of mitochondrial respiratory chain complexes I, IV, V, and increased neuronal maximal respiration capacity. NPCT exerted multiple neurotrophic effects including facilitating synaptogenesis, neuritogenesis, spinogenesis, and suppression of caspase-3. A polyclonal NPCT immunoneutralization antibody was developed to antagonize NPCT. In the in vitro 0-Mg2+ seizure model, immunoneutralization of NPCT caused more neuronal death, while exogenous NPCT supplementation, though did not reverse death outcomes, preserved mitochondrial membrane potential. In rat RSE model, both peripheral and intracerebroventricular immunoneutralization of NPCT exacerbated hippocampal neuronal death and peripheral immunoneutralization increased mortality. Intracerebroventricular immunoneutralization of NPCT further led to more serious hippocampal ATP depletion, and significant EEG power exhaustion. We conclude that NPCT is a neuropeptide regulating neuronal OXPHOS. During RSE, NPCT was overexpressed to protect hippocampal neuronal survival via facilitating energy supply.

The comparative effectiveness of metformin and risperidone in a rat model of valproic acid-induced autism, Potential role for enhanced autophagy

RationaleRisperidone is the first antipsychotic to be approved by Food and Drug Administration (FDA) for treating autism spectrum disorder (ASD). The potential efficacy of metformin in preventing and/or controlling ASD behavioral deficits was also recently reported. Suppression of hippocampus autophagy was suggested as a potential pathologic mechanism in ASD.ObjectivesIs metformin’s ability to improve ASD clinical phenotype driven by its autophagy-enhancing properties? And does hippocampus autophagy enhancement underlie risperidone’s efficacy as well? Both questions are yet to be answered.MethodsThe effectiveness of metformin on alleviation of ASD-like behavioral deficits in adolescent rats exposed prenatally to valproic acid (VPA) was compared to that of risperidone. The potential modulatory effects of risperidone on hippocampal autophagic activity were also assessed and compared to those of metformin.ResultsMale offspring exposed to VPA during gestation exhibited marked anxiety, social impairment and aggravation of stereotyped grooming; such deficits were efficiently rescued by postnatal risperidone or metformin therapy. This autistic phenotype was associated with suppressed hippocampal autophagy; as evidenced by reduced gene/dendritic protein expression of LC3B (microtubule-associated proteins 1 light chain 3B) and increased somatic P62 (Sequestosome 1) protein aggregates. Interestingly, compared to risperidone, the effectiveness of metformin in controlling ASD symptoms and improving hippocampal neuronal survival was well correlated to its ability to markedly induce pyramidal neuronal LC3B expression while lowering P62 accumulation.ConclusionsOur work highlights, for the first time, positive modulation of hippocampus autophagy as potential mechanism underlying improvements in autistic behaviors, observed with metformin, as well as risperidone, therapy.

KNT-127, a selective delta opioid receptor agonist, shows beneficial effects in the hippocampal dentate gyrus of a chronic vicarious social defeat stress mouse model

Delta opioid receptors (DOPs) play an important role in depression and other mood disorders. However, little is known about the underlying physiological mechanisms. The hypothalamic–pituitary–adrenal axis, adult hippocampal neurogenesis, and neuroinflammation are regarded as key pathophysiological factors in depression. In this study, we investigated the influence of DOP activation on those factors in a valid animal model of depression, chronic vicarious social defeat stress (cVSDS) mice. cVSDS mice (male C57BL/6J mice) were produced following a 10-day exposure to witness of social defeat stress, and each evaluation was performed more than 28 days after the stress period. Repeated administrations to cVSDS mice with a selective DOP agonist, KNT-127, both during (10 days) and after (28 days) the stress period respectively improved their decreased social interaction behaviors and increased serum corticosterone levels. When administered during the stress period, KNT-127 suppressed decreases in the hippocampal newborn neuron survival rate in cVSDS mice. Moreover, in both administration paradigms, KNT-127 reduced the number of Iba-1- and CD11b-positive cells in the subgranular zone and the granule cell layer of the hippocampal dentate gyrus, indicating a suppression of cVSDS-induced microglial overactivation. These results suggest that KNT-127 acts over the hypothalamic–pituitary–adrenal axis and regulates neurogenesis and neuroinflammation resulting in anti-stress effects, and the antidepressant-like effects of the DOP agonist are implicated in the suppression of the neuroinflammation. This study presents a new finding on the effects of repeated DOP activations on the pathophysiological states of depression.

Environmental Enrichment and Metformin Improve Metabolic Functions, Hippocampal Neuron Survival, and Hippocampal-Dependent Memory in High-Fat/High-Sucrose Diet-Induced Type 2 Diabetic Rats

Background: The Western-style diet-induced type 2 diabetes mellitus (T2D) may eventually trigger neurodegeneration and memory impairment. Thus, it is essential to identify effective therapeutic strategies to overcome T2D complications. This study aimed to investigate the effects of environmental enrichment (EE) and metformin interventions on metabolic dysfunctions, hippocampal neuronal death, and hippocampal-dependent memory impairments in high-fat/high-sucrose (HFS) diet-induced T2D rats. Methods: Thirty-two male rats (200-250 g) were divided into four groups: C group (standard diet + conventional cage); D group (HFS diet + conventional cage); DE group (HFS diet + EE cage/6hr daily); and DM group (HFS diet + metformin + conventional cage). Body weight was measured every week. T-maze tasks, anthropometric, biochemical, histological, and morphometric parameters were measured. The expression changes of hippocampal genes were also analyzed. Results: The anthropometric and biochemical parameters were improved in DE and DM groups compared with the D group. DE and DM groups had significantly higher T-maze percentages than the D group. These groups also had better histological and morphometric parameters than the D group. The interventions of EE and metformin enhanced the expression of hippocampal genes related to neurogenesis and synaptic plasticity (BDNF/TrkB binding, PI3K-Akt, Ras-MAPK, PLCγ-Ca2+, and LTP). Conclusion: Environmental enrichment (EE) and metformin improved metabolic functions, hippocampal neuron survival, and hippocampal-dependent memory in HFS diet-induced T2D rats. The underlying mechanisms of these interventions involved the expression of genes that regulate neurogenesis and synaptic plasticity.

Post-stroke periodic estrogen receptor-beta agonist improves cognition in aged female rats

Women have a higher risk of having an ischemic stroke and increased cognitive decline after stroke as compared to men. The female sex hormone 17β-estradiol (E2) is a potent neuro- and cognitive-protective agent. Periodic E2 or estrogen receptor subtype-beta (ER-β) agonist pre-treatments every 48 h before an ischemic episode ameliorated ischemic brain damage in young ovariectomized or reproductively senescent (RS) aged female rats. The current study aims to investigate the efficacy of post-stroke ER-β agonist treatments in reducing ischemic brain damage and cognitive deficits in RS female rats. Retired breeder (9–10 months) Sprague–Dawley female rats were considered RS after remaining in constant diestrus phase for more than a month. The RS rats were exposed to transient middle cerebral artery occlusion (tMCAO) for 90 min and treated with either ER-β agonist (beta 2, 3-bis(4-hydroxyphenyl) propionitrile; DPN; 1 mg/kg; s.c.) or DMSO vehicle at 4.5 h after induction of tMCAO. Subsequently, rats were treated with either ER-β agonist or DMSO vehicle every 48 h for ten injections. Forty-eight hours after the last treatment, animals were tested for contextual fear conditioning to measure post-stroke cognitive outcome. Neurobehavioral testing, infarct volume quantification, and hippocampal neuronal survival were employed to determine severity of stroke. Periodic post-stroke ER-β agonist treatment reduced infarct volume, improved recovery of cognitive capacity by increasing freezing in contextual fear conditioning, and decreased hippocampal neuronal death in RS female rats. These data suggest that periodic post-stroke ER-β agonist treatment to reduce stroke severity and improve post-stroke cognitive outcome in menopausal women has potential for future clinical investigation.

ATF6β Deficiency Elicits Anxiety-like Behavior and Hyperactivity Under Stress Conditions.

Activating transcription factor 6 (ATF6) is an endoplasmic reticulum (ER) stress-regulated transcription factor that induces expression of major molecular chaperones in the ER. We recently reported that ATF6β, a subtype of ATF6, promoted survival of hippocampal neurons exposed to ER stress and excitotoxicity, at least in part by inducing expression of calreticulin, an ER molecular chaperone with high Ca2+-binding capacity. In the present study, we demonstrate that ATF6β deficiency in mice also decreases calreticulin expression and increases expression of glucose-regulated protein 78, another ER molecular chaperone, in emotional brain regions such as the prefrontal cortex (PFC), hypothalamus, hippocampus, and amygdala. Comprehensive behavioral analyses revealed that Atf6b-/- mice exhibit anxiety-like behavior in the light/dark transition test and hyperactivity in the forced swim test. Consistent with these results, PFC and hypothalamic corticotropin-releasing hormone (CRH) expression was increased in Atf6b-/- mice, as was circulating corticosterone. Moreover, CRH receptor 1 antagonism alleviated anxiety-like behavior in Atf6b-/- mice. These findings suggest that ATF6β deficiency produces anxiety-like behavior and hyperactivity via a CRH receptor 1-dependent mechanism. ATF6β could play a role in psychiatric conditions in the emotional centers of the brain.