Cognitive Impairment In Aged Rats Research Articles

Involvement of Fgf2-mediated tau protein phosphorylation in cognitive deficits induced by sevoflurane in aged rats

ObjectiveAnesthetics have been linked to cognitive alterations, particularly in the elderly. The current research delineates how Fibroblast Growth Factor 2 (Fgf2) modulates tau protein phosphorylation, contributing to cognitive impairments in aged rats upon sevoflurane administration.MethodsRats aged 3, 12, and 18 months were subjected to a 2.5% sevoflurane exposure to form a neurotoxicity model. Cognitive performance was gauged, and the GEO database was employed to identify differentially expressed genes (DEGs) in the 18-month-old cohort post sevoflurane exposure. Bioinformatics tools, inclusive of STRING and GeneCards, facilitated detailed analysis. Experimental validations, both in vivo and in vitro, examined Fgf2’s effect on tau phosphorylation.ResultsSevoflurane notably altered cognitive behavior in older rats. Out of 128 DEGs discerned, Fgf2 stood out as instrumental in regulating tau protein phosphorylation. Sevoflurane exposure spiked Fgf2 expression in cortical neurons, intensifying tau phosphorylation via the PI3K/AKT/Gsk3b trajectory. Diminishing Fgf2 expression correspondingly curtailed tau phosphorylation, neurofibrillary tangles, and enhanced cognitive capacities in aged rats.ConclusionSevoflurane elicits a surge in Fgf2 expression in aging rats, directing tau protein phosphorylation through the PI3K/AKT/Gsk3b route, instigating cognitive aberrations.

Carnosol ameliorates sevoflurane induced cognitive impairment in aged rats by suppressing NLRP3 inflammasome via activation of autophagy

Purpose: To investigate the effect of carnosol on the progression of postoperative cognitive dysfunction (POCD) and to elucidate its mechanism of action.
 Methods: A cognitive impairment model rat induced by sevoflurane (SEV) was established. Dihydroethidium (DHE) assay was conducted to determine the effect of carnosol on reactive oxygen species (ROS) levels in sevoflurane-induced rats. Adenosine triphosphate (ATP) production and immunoblot assays were used to assess carnosol effect on mitochondrial damage, while water maze experiment was performed to evaluate cognitive dysfunction in the rats. The mechanism of action was investigated using immunoblot assay.
 Results: Carnosol suppressed sevoflurane-induced ROS production in the rats, and alleviated sevoflurane-induced mitochondrial damage; it also activated autophagy. Furthermore, carnosol suppressed SEV-induced NLRP3 inflammasome activation by activating autophagy and suppressing SEV-induced cognitive dysfunction via the suppression of NLRP3 inflammasome activation.
 Conclusion: Carnosol ameliorates SEV-stimulated cognitive impairment by suppressing NLRP3 inflammasome and thus, can potentially be developed serve as a therapeutic agent for the management of cognitive impairment.

Retraction: Young plasma reverses anesthesia and surgery-induced cognitive impairment in aged rats by modulating hippocampal synaptic plasticity.

[This retracts the article DOI: 10.3389/fnagi.2022.996223.].

C/EBPα involvement in microglial polarization via HDAC1/STAT3 pathway aggravated sevoflurane-induced cognitive impairment in aged rats.

Postoperative cognitive dysfunction (POCD) is a clinically frequent postoperative complication in the elderly, which is mainly manifested by the occurrence of cognitive dysfunction after anesthetized surgery in patients. To explore the involvement of C/EBPα in microglial polarization in sevoflurane anesthesia induced cognitive impairment in aged rats. Sprague-Dawley (SD) rats were anesthetized by inhalation of 3% sevoflurane for 6 h to establish the POCD model. The histopathological structure of hippocampus was observed by hematoxylin and eosin (HE) staining. Associative learning and memory function and spatial learning and memory function were assessed by conditioned fear test and water maze test. The concentrations of inflammatory factors in the hippocampus were measured by ELISA. The levels of microglial activation marker (Iba1) and microglial M1 (CD86) and M2 (CD206) polarization markers were determined by immunofluorescence staining and RT-qPCR, respectively. The transcriptional regulation of HDAC1 by C/EBPα was confirmed by dual luciferase reporter assay and ChIP assay. Sevoflurane-induced pathomorphological damage in the hippocampal tissue of aged rats, accompanied by elevated expression of C/EBPα. Silencing of C/EBPα alleviated hippocampal histopathological injury, inhibited M1 microglial activation and the expression of M1 marker CD86, enhanced the expression of M2 marker CD206. C/EBPα transcriptionally activated HDAC1. Knockdown of C/EBPα downregulated the expression of HDAC1 and STAT3 phosphorylated proteins, which inhibited the pro-inflammatory factors (IL-6 and TNF-α) and accelerated anti-inflammatory factors (IL-10 and TGF-β) secretion. In addition, silencing of C/EBPα caused rats to have a delayed freezing time in contextual conditioned fear, a shorter escape latency, and an increased number of platform crossings. Inhibition of C/EBPα promotes the M2 polarization of microglia and reduces the production of pro-inflammatory cytokines to alleviate the cognitive dysfunction of sevoflurane-induced elderly rats by HDAC1/STAT3 pathway.

Rapamycin Affects the Hippocampal SNARE Complex to Alleviate Cognitive Dysfunction Induced by Surgery in Aged Rats.

Delayed neurocognitive recovery (dNCR) is a common complication that occurs post-surgery, especially in elderly individuals. The soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex plays an essential role in various membrane fusion events, such as synaptic vesicle exocytosis and autophagosome-lysosome fusion. Although SNARE complex dysfunction has been observed in several neurodegenerative disorders, the causal link between SNARE-mediated membrane fusion and dNCR remains unclear. We previously demonstrated that surgical stimuli caused cognitive impairment in aged rats by inducing α-synuclein accumulation, inhibiting autophagy, and disrupting neurotransmitter release in hippocampal synaptosomes. Here, we evaluated the effects of propofol anesthesia plus surgery on learning and memory and investigated levels of SNARE proteins and chaperones in hippocampal synaptosomes. Aged rats that received propofol anesthesia and surgery exhibited learning and memory impairments in a Morris water maze test and decreased levels of synaptosome-associated protein 25, synaptobrevin/vesicle-associated membrane protein 2, and syntaxin 1. Levels of SNARE chaperones, including mammalian uncoordinated-18, complexins 1 and 2, cysteine string protein-α, and N-ethylmaleimide-sensitive factor, were all significantly decreased following anesthesia with surgical stress. However, the synaptic vesicle marker synaptophysin was unaffected. The autophagy-enhancer rapamycin attenuated structural and functional disturbances of the SNARE complex and ameliorated disrupted neurotransmitter release. Our results indicate that perturbations of SNARE proteins in hippocampal synaptosomes may underlie the occurrence of dNCR. Moreover, the protective effect of rapamycin may partially occur through recovery of SNARE structural and functional abnormalities. Our findings provide insight into the molecular mechanisms underlying dNCR.

Activation of α7nAChR by PNU282987 improves cognitive impairment through inhibiting oxidative stress and neuroinflammation in D-galactose induced aging via regulating α7nAChR/Nrf2/HO-1 signaling pathway

Aging is an important risk factor for neurodegenerative diseases. The activation of α7 nicotinic acetylcholine receptor (α7nAChR) is involved in inflammation and cognition, but the specific role it plays in aging remains unknown. This study aimed to investigate the anti-aging effect of the activation of α7nAChR on aging rats and BV2 cells induced by D-galactose, as well as its potential mechanism. D-galactose induced an increase in the SA-β-Gal positive cells, expression of p16 and p21 in vivo and in vitro. α7nAChR selective agonist PNU282987 decreased levels of pro-inflammatory factors, MDA, and Aβ, enhanced SOD activity and levels of anti-inflammatory factor (IL10) in vivo. PNU282987 enhanced the expression of Arg1, decreased the expression of iNOS, IL1β and TNFα in vitro. PNU282987 upregulated the levels of α7nAChR, Nrf2 and HO-1 in vivo and in vitro. The results of Morris water maze and novel object recognition tests showed that PNU282987 improved cognitive impairment in aging rats. Furthermore, α7nAChR selective inhibitor methyllycaconitine (MLA) results were opposite with PNU282987. PNU282987 improves cognitive impairment through inhibiting oxidative stress and neuroinflammation in D-galactose induced aging via regulating the α7nAChR/Nrf2/HO-1 signaling pathway. Therefore, targeting the α7nAChR may be a viable therapeutic approach for anti-inflammaging and neurodegenerative diseases.

Activation of autophagy inhibits the activation of NLRP3 inflammasome and alleviates sevoflurane-induced cognitive dysfunction in elderly rats

Aims/introductionAs a common complication in elderly patients after surgery/anesthesia, postoperative cognitive dysfunction (POCD) is mainly characterized by memory, attention, motor, and intellectual retardation. Neuroinflammation is one of the most uncontroversial views in POCD. The sevoflurane-induced neurotoxicity has attracted widespread attention in recent years. However, its mechanism has not been determined. This study aimed to observe the effects of sevoflurane on cognitive function and the changes in inflammatory indices and autophagy protein expression in the prefrontal cortex in aged rats.MethodBefore the experiment, D-galactose was diluted with normal saline into a liquid with a concentration of 125 mg/kg and injected subcutaneously into the neck and back of rats for 42 days to establish the aging rat model. Morris water maze experiments were performed, including positioning navigation (5 days) and space exploration (1 day). The POCD model was established by 3.2% sevoflurane inhalation. The rats were treated with or without MCC950, a potent and selective nucleotide‐binding oligomerization domain‐like receptor protein 3 (NLRP3) inhibitor, followed by autophagy agonists and autophagy inhibitors. The expression levels of inflammasome-related protein NLRP3 and autophagy-related proteins LC3B and P62 were detected to test the behavior of rats with a water maze.ResultsWe found that sevoflurane exposure affected learning and working memory ability in aged rats. We also observed microglia activation in the prefrontal cortex. NLRP3 protein expression was significantly upregulated after sevoflurane inhalation. NLRP3 inflammasome activation induced increased expression and mRNA expression of cleaved Caspase-1 and inflammatory cytokines IL-1β and IL-18, and increased secretion of peripheral proinflammatory cytokines. The inhibitor MCC950 was used to improve cognitive ability and inflammation in rats and inhibit the secretion of cytokines. In addition, we demonstrated that significant inhibition of autophagy (decreased LC3-II/I and increased P62) was accompanied by increased activation of NLRP3 inflammasomes and more severe neural cell damage. However, autophagy inhibitor rapamycin administration to activate autophagy resulted in the inhibition of NLRP3 inflammasomes, ultimately attenuating neuronal injury.ConclusionsThe activation of autophagy suppressed the formation of NLRP3 inflammasomes. It also alleviated cognitive impairment in aged rats.

Young plasma reverses anesthesia and surgery-induced cognitive impairment in aged rats by modulating hippocampal synaptic plasticity.

We investigated the protective effect of young plasma on anesthesia- and surgery-induced cognitive impairment and the potential underlying mechanism using bioinformatics, functional enrichment analysis, gene set enrichment analysis, Golgi-Cox staining, dendritic spine analysis, immunofluorescence assay, western blot analysis, and transmission electron microscopy. Furthermore, we performed behavioral assessments using the open field test, the novel object recognition test, and the Morris water maze test. We identified 1969 differentially expressed genes induced by young plasma treatment, including 800 upregulated genes and 1169 downregulated genes, highlighting several enriched biological processes (signal release from synapse, postsynaptic density and neuron to neuron synapse). Anesthesia- and surgery-induced cognitive impairment in aged rats was comparatively less severe following young plasma preinfusion. In addition, the decreased levels of synapse-related and tyrosine kinase B/extracellular signal-regulated protein kinase/cyclic adenosine monophosphate response element-binding protein (TrkB/ERK/CREB) signaling pathway-related proteins, dendritic and spine deficits, and ultrastructural changes were ameliorated in aged mice following young plasma preinfusion. Together, these findings suggest that young plasma reverses anesthesia- and surgery-induced cognitive impairment in aged rats and that the mechanism is associated with the activation of the TrkB/ERK/CREB signaling pathway and improvement in hippocampal synaptic plasticity.

The major anthocyanin of Lycium ruthenicum Murr. relieves cognitive deficits, oxidative stress, neuroinflammation, and hippocampal metabolome alterations in aging rats

• Pn3G5G is the most abundant anthocyanin in LRF. • Long term administration of Pn3G5G improved cognitive impairment of aging rats. • Pn3G5G reduced hippocampal pathologic changes, oxidative stress, and inflammation. • Pn3G5G effectively restored the abnormal hippocampal metabolites in aging rats. Lycium ruthenicum Murr. fruit (LRF) is a functional food that abundant in anthocyanins. In this study, the neuroprotection of the major anthocyanin in LRF, namely petunidin-3,5-O-diglucosides (Pn3G5G), was investigated in D-galactose-induced aging rats. Our results showed that administration of Pn3G5G by oral gavage (100 mg/kg·bw) for 7 weeks did not influence the body weight and motor function of rats. More importantly, Pn3G5G could relieve cognitive deficits, mitigate cortical and hippocampal neuron loss, reduce the levels of aging-related markers (AGEs and MDA), increase the ratio of GSH/GSSG, and suppress neuroinflammation in the hippocampus. LC-MS-based metabolomics revealed that Pn3G5G could restore the altered hippocampal metabolic profile. In total, 39 differential metabolites and 47 pathways were involved. Particularly, Pn3G5G corrected amino acid metabolic problems by restoring the levels of L-cystine, L-histidine, L-serine, S-sulfo-L-cysteine, L-asparagine, glutathione (reduced form), L-saccharopine, N-acetyl-L-leucine, 5-oxoproline (pyroglutamic acid), 3-N-methyl-L-histidine and N-methyl-L-glutamate to protect neurons from oxidative stress and inflammatory damage. Besides, Pn3G5G also regulate ABC transporters, protein digestion and absorption, and biosynthesis of cofactors to prevent abnormal energy metabolism of neurons. In conclusion, Pn3G5G likely enhance antioxidant and anti-inflammatory defenses, as well as maintain normal function of hippocampus through influencing these metabolic pathways, thereby alleviating cognitive impairment in aging rats.

Hypercholesterolemia aggravates sevoflurane-induced cognitive impairment in aged rats by inducing neurological inflammation and apoptosis.

We aimed to explore the effects of hypercholesterolemia on sevoflurane-induced cognitive impairment in aged rats and the underlying mechanism(s). Aged rats were administrated with high-fat diet, sevoflurane, or both. Thereafter, the plasma levels of total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL), and high-density lipoprotein (HDL) were evaluated. The Morris water maze task was performed to evaluate the spatial learning and memory ability of rats. Moreover, Nissl and Evans blue staining were conducted to test nerve damage and detect the blood-brain barrier permeability, respectively. The percentage of apoptotic cells was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling assay. The messenger RNA expression of inflammatory factors and protein expression of microglial activation markers and apoptosis-related proteins were tested by real-time polymerase chain reaction, enzyme-linked immunosorbent assay, or western blot analysis, respectively. High-fat diet induced high levels of TC, TG, and LDL but decreased levels of HDL. However, sevoflurane had no effects on these levels. In contrast, sevoflurane significantly induced the impairment of learning and memory, nerve damage, neuroinflammatory damage, and neuronal apoptosis. Hypercholesterolemia exacerbated the sevoflurane-induced impairment in aged rats. These results suggested that hypercholesterolemia aggravates sevoflurane-induced cognitive impairment in aged rats, possibly by inducing neurological inflammation and apoptosis.

Electroacupuncture relieves postoperative cognitive dysfunction in elderly rats via regulating amp-activated protein kinase autophagy signaling.

Postoperative cognitive dysfunction (POCD) is a common complication after surgery in elderly patients. Electroacupuncture (EA) has been reported to relieve POCD in animal models, but the mechanism remains fully elucidated. The objective of this work was to clarify whether EA could alleviate POCD via regulating autophagy. In this study, aged rats were assigned into 4 groups: control, surgery (rats underwent exploratory laparotomy to induce POCD), EA + S (rats received EA pre-stimulation before surgery), and EA + S + Chloroquine (CQ) (rats were intraperitoneally injected with CQ before EA stimulation and then underwent surgery). The cognitive function of rats was assessed by Morris Water Maze (MWM) test after surgery, and autophagy in hippocampal tissues of rats was evaluated by western blotting and transmission electron microscope. Results indicated that the MWM test revealed that rats showed reduced platform crossing and increased total swimming distance after surgery. However, this impaired spatial memory was improved by EA and EA plus CQ pre-treatment. Besides, the surgery caused an increased expression in LC3II, Beclin-1, AMP-activated protein kinase (AMPK), and p-AMPK in hippocampal tissues of rats, while EA and EA plus CQ pre-treatment also reversed this effect. In addition, the surgery-induced increased amount of autophagic vesicles in hippocampal tissues of rats was reduced by EA and EA plus CQ pre-treatment. In conclusion, EA pre-stimulation could effectively attenuate cognitive impairment in aged rats with POCD via inhibiting AMPK signaling-mediated autophagy.

Lovastatin attenuates sevoflurane-induced cognitive disorder in aged rats via reducing Aβ accumulation

As a general anesthetic widely used in surgical, sevoflurane has been shown to cause cognitive and memory deficits in the elderly. It's important to find out agents that can counteract sevoflurane-induced cognitive dysfunction. This study is aimed to investigate the effect of lovastatin on sevoflurane-induced cognitive impairment in aged rats and reveal the potential mechanisms. BV-2 cells, rat hippocampal neurons or male aged rats were exposed to 2% sevoflurane for 5 h. The cells were pretreated with 10 μM lovastatin. The rats were intraperitoneally injected with 5 mg/kg/day lovastatin for three days. The results showed that lovastatin enhanced exosomal IDE secretion from sevoflurane-exposed BV-2 cells and promoted Aβ degradation. Lovastatin treatment also inhibited the increased expressions of β-secretase 1 (BACE1) and γ-secretase in hippocampal neurons under sevoflurane exposure in vitro. In animal experiments, the discrimination index in novel object recognition test and percentage of spontaneous alternation in Y-maze test were significantly elevated after lovastatin administration. In addition, Aβ plaque area and contents of soluble Aβ1-40 and Aβ1-42 in the hippocampal tissues were decreased upon lovastatin treatment. Furthermore, lovastatin reversed sevoflurane-induced Aβ accumulation via up-regulating IDE expression, and down-regulating amyloid precursor protein (APP)-related protein expression (β-C-terminal fragment (CTF), BACE1 and γ-secretase). In conclusion, lovastatin alleviates sevoflurane-induced cognitive deficient in aged rats via promoting Aβ degradation and reducing Aβ production. Lovastatin may be beneficial in preventing anesthetic-induced cognitive impairment.

Apoptosis inhibition is involved in improvement of sevoflurane-induced cognitive impairment following normobaric hyperoxia preconditioning in aged rats.

Sevoflurane, a commonly used anesthetic agent has been confirmed to induce cognitive impairment in aged rats. Normobaric hyperoxia preconditioning has been demonstrated to induce neuroprotection in rats. The present study aimed to determine whether normobaric hyperoxia preconditioning could ameliorate cognitive deficit induced by sevoflurane and the possible mechanism by which it may exert its effect. A total of 66, 20-month-old male Sprague-Dawley rats were randomly divided into 3 groups (n=22 each): Rats in the control (C) and sevoflurane anesthesia (S) groups received no normobaric hyperoxia preconditioning before sevoflurane exposure, rats in the normobaric hyperoxia pretreatment (HO) group received normobaric hyperoxia preconditioning before sevoflurane exposure (95% oxygen for 4 continuous h daily for 6 consecutive days). The anesthesia rats (S and HO groups), were exposed to 2.5% sevoflurane for 5 h, while the sham anesthesia rats (C group) were exposed to no sevoflurane. The neurobehavioral assessment was performed using a Morris water maze test, the expressions of the apoptosis proteins were determined using western blot analysis, and the apoptosis rate and cytosolic calcium concentration were measured by flow cytometry. Normobaric hyperoxia preconditioning improved prolonged escape latency and raised the number of platform crossings induced by sevoflurane in the Morris water maze test, increased the level of bcl-2 protein, and decreased the level of bax and active caspase-3 protein, the apoptosis rate and cytosolic calcium concentration in the hippocampus 24 h after sevoflurane exposure. The findings of the present study may imply that normobaric hyperoxia preconditioning attenuates sevoflurane-induced spatial learning and memory impairment, and this effect may be partly related to apoptosis inhibition in the hippocampus. In conclusion, normobaric hyperoxia preconditioning may be a promising strategy against sevoflurane-induced cognitive impairment by inhibiting the hippocampal neuron apoptosis.

Preventive electroacupuncture reduces cognitive deficits in a rat model of D-galactose-induced aging.

Acupuncture can reduce cognitive deficits in Alzheimer's disease. However, whether electroacupuncture can prevent or alleviate the cognitive deficits in animal models of aging remains poorly understood. Studies have shown that disordered epigenetic modifications play a critical role in age-related cognitive decline. Therefore, we hypothesized that preventive electroacupuncture might improve cognitive functions during aging by regulating epigenetic modifications. A rat model of aging was produced by intraperitoneal injection of 120 mg/kg D-galactose for 8 weeks. Baihui and Shenshu acupoints were stimulated by electroacupuncture for 8 weeks from the first day of D-galactose administration. Preventive electroacupuncture alleviated memory impairment, decreased tau hyperphosphorylation, and reduced glycogen synthase kinase-3β protein and mRNA expression levels in the brainstem dorsal raphe nucleus, where intracellular neurofibrillary tangle lesions first occur. In addition, the DNA methylation level in the promoter region of the glycogen synthase kinase-3β gene was increased. The effects of preventive electroacupuncture were stronger than those of preventive acupuncture. Intraperitoneal injection of 0.4 mg/kg 5-aza-2'-deoxycytidine, an inhibitor of DNA methyltransferase that blocks epigenetic modifications, antagonized the effects of preventive electroacupuncture. Our results suggest that preventive electroacupuncture treatment alleviates cognitive impairment in aging rats probably by affecting the epigenetic modification of the glycogen synthase kinase-3β gene in the dorsal raphe nucleus. This study was approved by the Animal Ethics Committee of Hubei University of Chinese Medicine, China (approval No. HUCMS201712001) on November 28, 2017.

Repeated propofol exposure-induced neuronal damage and cognitive impairment in aged rats by activation of NF-κB pathway and NLRP3 inflammasome

BackgroundElderly patients receive propofol at regular intervals for sedation during gastrointestinal endoscopy. However, the link between cognition and intermittent propofol exposure remains unclear. Thus, we used aged rats to investigate the effect of propofol on cognition. MethodsThe study included two parts. In the first part, aged (18–20 months old) male Sprague-Dawley rats underwent intermittent intraperitoneal injection of propofol (200 mg/kg) or intralipid, every 9 days or once a day. In the second part, some aged rats received intraperitoneal injection of Bay 11-7082 (1 mg/kg), a specific inhibitor of NF-κB, 30 min before propofol injection. Memory tests were performed to evaluate cognition 24 h after the entire treatment. The hippocampal neuronal damage was assessed by TUNEL staining. The hippocampal levels of p-NF-κB p65, NLRP3, caspase-1 p20, and cleaved caspase-3 were detected by western blotting. The hippocampal and serum levels of IL-1β, IL-6, and TNF-α were evaluated using ELISA. ResultsThere were no differences in the behavioral tests, hippocampal neuronal damage, and neuroinflammation between groups given intralipid and propofol treatment every 9 days. However, repeated propofol treatment once a day promoted activation of NF-κB and the NLRP3 inflammasome, inducing cognitive impairment and neuroinflammation. Interestingly, pretreatment with Bay-11-7082 not only inhibited NF-κB/NLRP3 inflammasome activation, but also attenuated neuronal damage and cognitive dysfunction in aged rats exposed to daily propofol treatment. ConclusionsIntermittent propofol treatment every 9 days may be safe for aged rats. However, propofol treatment once a day could impair the cognition of aged rats, partly through the activation of the NF-κB pathway and NLRP3 inflammasome, which may be a potential targets for the treatment of cognitive impairment in elderly patients.

Discussion of the promising effect of electroacupuncture on cognitive improvement in D-galactose-induced aging rats based on NLRP3-ASC-Caspase-1 signaling pathway

To investigate the effect of electroacupuncture (EA) on cognitive function in D-galactose (D-gal)-induced aging rats, and the correlation between the effect and nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3)-ASC-Caspase-1 signaling pathway. Forty-six male Sprague-Dawley (SD) rats were randomly divided into a control group (n=10), a model group (n=12), an EA-7 d group (n=12) and an EA-21 d group (n=12). Except the control group, the other three groups received 42 consecutive days of intraperitoneal injection of D-gal to establish aging rat models with cognitive dysfunction. The control group received the same amount of normal saline via intraperitoneal injection. Two EA groups were given EA therapy for 21 consecutive days (began from the 22nd day of modeling) or 7 consecutive days (began from the 36th day of modeling) accordingly at Dazhui (GV 14), Baihui (GV 20), Shenshu (BL 23) and Zusanli (ST 36). After modeling/intervention, all four groups received behavioral evaluations by Morris water maze (MWM) test, novel object recognition (NOR) test and step-down passive avoidance (SDPA) test followed by the Western blot (WB) detection of the expression levels of hippocampal NLRP3 inflammasome-associated proteins NLRP3, ASC and Caspase-1. MWM (place navigation test, PNT) results showed that the escape latency in the model group was significantly longer than that in the other three groups (P 0.05). From the 2nd day to the 4th day of the test, there was no significant difference between the EA-21 d group and the control group (P>0.05) in the escape latency; the escape latency was significantly shorter in the EA-21 d group than in the model group and the EA-7 d group (P 0.05). NOR results showed that there was no significant difference in the recognition ratio between the EA-7 d group and the EA-21 d group (P>0.05), and the recognition ratio was significantly higher in the two EA groups than in the model group (P 0.05). The model group had the shortest step-down latency, followed by the EA-7 d group, the EA-21 d group and the control group in order (P 0.05). NLRP3 inflammasome may be involved in the development of cognitive decline in aging rats; 7 consecutive days of EA intervention can partially improve the cognitive impairment in aging rats though the effect is rather limited; 21 consecutive days of EA intervention may improve the learning and memory abilities in aging rats via down-regulating the expression levels of NLRP3 inflammasome-associated proteins in hippocampus.

Hirsutanol A exhibits neuroprotective activities against sevoflurane-induced neurotoxicity in aged rats.

The neurotoxicity of the inhaled anesthetic, sevoflurane, has been documented in a number of studies. In this study, we conducted experiments to investigate whether Hirsutanol A (HA), a sesquiterpene compound from the fungus, Chondrostereum sp., can provide protection from sevoflurane-induced neurological toxicity in aged rats, and analyzed the underlying mechanisms. The cognitive dysfunction of rats following sevoflurane exposure was evaluated by behavioral tests. The neuronal cell survival was determined by Nissl staining. In addition, human neuroblastoma H4 cells were exposed to sevoflurane to establish an in vitro model. Apoptotic marker expression in hippocampal tissue was determined by western blotting. Cell apoptosis in vitro was also examined by TUNEL assay and flow cytometry. The expression and translocation of Nrf2 were examined by both western blot and immunofluorescence staining. Our results show that HA significantly attenuated sevoflurane-induced cognitive impairment in aged rats. In addition, HA treatment decreased sevoflurane-induced neuronal apoptosis in the hippocampus and alleviated Aβ accumulation. Our results also show that the neuroprotective effect of HA is associated with the activation of Nrf2 signaling. Human neuroblastoma H4 cells were used as a model to examine the protective activity of HA against sevoflurane-induced neurotoxicity. In addition, our results show that the inhibition of Nrf2 by a specific inhibitor or targeting siRNA significantly compromises the attenuating effect of HA on sevoflurane-induced cell apoptosis and Aβ accumulation. Our results suggest that HA may function as a neuroprotective agent against sevoflurane-induced neurotoxicity.

Neuroprotective effect of DUSP14 overexpression against isoflurane-induced inflammatory response, pyroptosis and cognitive impairment in aged rats through inhibiting the NLRP3 inflammasome.

Postoperative cognitive dysfunction (POCD) is a common complication after general anesthesia in the elderly people. Dual-specificity phosphatase 14 (DUSP14, also known as MKP6) has been implicated in the pathogenesis of various inflammatory diseases. However, the exact role and mechanism of DUSP14 in POCD remains unclear. An isoflurane exposure induced POCD aged rat model was successfully constructed. The pathological changes of hippocampal tissues of aged rats were detected by Nissl staining. Evaluation of learning and memory abilities in aged rats was measured using Morris water maze task test. The DUSP14 level was detected by immunohistochemistry (IHC) assay, quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) and Western blot, respectively. Levels of brain injury markers [S-100β and neuron specific enolase (NSE)] and inflammatory cytokines [interleukin (IL)-1β (tumor necrosis factor (TNF)-α and IL-6] were detected using Enzyme Linked Immunosorbent Assay (ELISA) or qRT-PCR. The apoptosis of hippocampal nerve cells was assessed by Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay. Western blot assay was used to measure the expression of proteins related to apoptosis, pyroptosis and NOD-like receptor family pyrin domain-containing 3 (NLRP3)-Caspase-1 pathway. Isoflurane exposure led to brain injury, inflammatory response, cognitive dysfunction in aged rats and decreased the expression of DUSP14. Overexpression of DUSP14 could inhibit apoptosis, inflammation, pyroptosis, brain tissue damage, and improve cognitive dysfunction of aged rats after isoflurane anesthesia. Further mechanism studies revealed that DUSP14 may play a neuroprotective effect on POCD by regulating NLRP3 inflammasome-mediated pyroptosis. DUSP14 may effectively protect against isoflurane-induced neuro-inflammation, brain damage and cognitive dysfunction, indicating that DUSP14 may be a potential predictor and therapeutic target for POCD.

Yizhi Qingxin Formula Extract Ameliorates Cognitive Decline in Aged Rats via the Brain-Derived Neurotrophic Factor/Tropomyosin Receptor Kinase B Pathway.

Cognitive impairment and decline in old age are primarily driven by the accumulation of age-related neuropathologies, and old age is thus the primary risk factor for neurodegenerative diseases such as AD. Here, we investigated the effects of Yizhi Qingxin formula (YQF) extract on cognitive impairment in aged rats and determine the role of the brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB) pathway underlying the neuroprotective effects of the YQF extract. Fifty male Wistar rats were randomly divided into five groups: Control group, Model group, Donepezil group, and YQF extract groups (treatment with YQF extract at two different doses). After treatment with YQF extract for 8 weeks, learning and cognitive abilities were assessed using the Morris water maze. Morphological changes in the hippocampus were observed using hematoxylin-eosin. Activated microglia and astrocytes were assessed using immunohistochemistry. Expressions of proteins and genes were examined using western blotting and real-time PCR. The results revealed that oral treatment with YQF extract dramatically improved spatial learning and memory ability and ameliorated histopathological and morphological characteristics in aged rats. YQF extract significantly increased acetylcholine and interleukin (IL)-10 levels but markedly decreased amyloid-β peptide, tumor necrosis factor alpha (TNFα), IL-2, and IL-6 levels. In addition, it inhibited the excessive activation of microglia and astrocytes, downregulated the expressions of TNFα and IL-2, and upregulated nerve growth factor, BDNF, and TrkB expressions. Furthermore, hippocampal extracellular signal-related kinase (Erk) and protein kinase B (Akt), the upstream signaling of BDNF/TrkB, were also activated by treatment with YQF extract. Our findings indicate that YQF extract activates the BDNF/TrkB pathway through the upregulation of Erk and Akt signaling, and the activated signaling pathway might contribute to the protective effects of YQF extract on cognitive impairment in aged rats.

Capsosiphon fulvescens Glycoproteins Enhance Probiotics-Induced Cognitive Improvement in Aged Rats.

Aging-induced cognitive dysfunction can be regulated by probiotics through bidirectional communication with the brain. This study aimed to investigate whether Capsosiphon fulvescens glycoproteins (Cf-hGP) enhanced probiotic-induced improvement of memory in aged rats and the underlying mechanism in the dorsal hippocampus. Cf-hGP were isolated using lectin resin. Cf-hGP (15 mg/kg/day) and/or Lactobacillus plantarum (L. plantarum) (109 CFU/rat/day) were orally administered once a day for 4 weeks. Co-treatment with Cf-hGP and L. plantarum synergistically improved spatial memory in aged rats, which was overturned by functional blocks of brain-derived neurotrophic factor (BDNF) signaling. Increases in BDNF expression and nuclear factor erythroid 2-related factor 2 (Nrf2) phosphorylation were accompanied by mono- and/or co-administration in the dorsal hippocampus, while c-Jun N-terminal kinase (JNK) phosphorylation and glucose-regulated protein 78 expression were decreased. These synergistic effects were downregulated by blocks of BDNF/Nrf2-mediated signaling. In particular, co-treatment, not mono-treatment, reduced phosphorylation of eukaryotic elongation factor 2 (eEF2) regulated by eEF2 kinase and protein phosphatase 2A. Additionally, co-treatment downregulated the interaction between eEF2 kinase and JNK. These data demonstrated that cognitive impairment in aged rats was synergistically diminished by co-treatment with Cf-hGP and L. plantarum through BDNF-mediated regulation of Nrf2 and eEF2 signaling pathways in the dorsal hippocampus.