Decrease of glial cell-derived neurotrophic factor contributes to anesthesia- and surgery-induced learning and memory dysfunction in neonatal rats

GDNF facilitates cognitive function recovery following neonatal surgical-induced learning and memory impairment via activation of the RET pathway and modulation of downstream effectors PKMζ and Kalirin in rats

OBJECTIVE

The aim of this study is to elucidate the underlying mechanism through which glial cell line-derived neurotrophic factor (GDNF) improves cognitive deficits in adults resulting from neonatal surgical interventions.

METHODS

Newborn Sprague-Dawley rats, regardless of gender, were randomly allocated into seven groups on postnatal day 7 as follows (n=15): (1) Control group (not subjected to anesthesia, surgery, or any pharmaceutical interventions); (2) GDNF group (received intracerebroventricular injection of GDNF); (3) Surgery group (underwent right carotid artery exposure under anesthesia with 3% sevoflurane); (4) Surgery plus GDNF group; (5) Surgery plus GDNF and type II JAK inhibitor NVP-BBT594 (BBT594) group (administered intraperitoneal injection of BBT594); (6) BBT group; and (7) Surgery plus BBT group. Starting from postnatal day 33, all rats underwent Barnes maze and fear conditioning tests, followed by decapitation under sevoflurane anesthesia for subsequent analyses. The left hemibrains underwent Golgi staining, while the right hemibrains were used for hippocampal protein extraction to assess Protein kinase Mζ (PKMζ) and Kalirin expression through western blotting.

RESULTS

GDNF demonstrated a mitigating effect on spatial learning and memory impairment, as well as context-related fear memory impairment, reductions in dendritic total lengths, and spinal density within the hippocampus induced by surgical intervention. Notably, all of these ameliorative effects of GDNF were reversed upon administration of the RET inhibitor BBT594. Additionally, GDNF alleviated the downregulation of protein expression of PKMζ and Kalirin in the hippocampus of rats subjected to surgery, subsequently reversed by BBT594.

CONCLUSION

The effective impact of GDNF on learning and memory impairment caused by surgical intervention appears to be mediated through the RET pathway. Moreover, GDNF may exert its influence by upregulating the expression of PKMζ and Kalirin, consequently enhancing the development of dendrites and dendritic spines.

Astrocytic GDNF ameliorates anesthesia and surgery-induced cognitive impairment by promoting hippocampal synaptic plasticity in aged mice

BACKGROUND

Perioperative neurocognitive disorders (PND) are common complications after surgery in older patients. However, the specific mechanism of this condition remains unclear. Glial cell line-derived neurotrophic factor (GDNF) is an important neurotrophin that abundantly expressed throughout the brain. It can enhance synaptic plasticity and alleviate learning and memory impairments. Thus, the purpose of this study was to investigate the role of GDNF in PND and the mechanisms involved.

METHODS

The PND animal model was established by performing left tibial fracture surgery on 18-month-old C57BL/6 mice under sevoflurane anesthesia. Recombinant adeno-associated virus (rAAV)-GDNF or empty vectors were injected bilaterally into the hippocampal CA1 region of aged mice 3 weeks before anesthesia/surgery. The open field and fear conditioning test were used to assess the behavior changes. Golgi staining and electrophysiology were utilized to evaluate the morphological and functional alterations of neuronal synaptic plasticity. Western blot analysis was carried out to measure the proteins expression levels and immunofluorescence staining was performed to probe the cellular localization of GDNF.

RESULTS

Mice with surgery and anesthesia showed a significant decrease in hippocampus-dependent learning and memory, accompanied by a decline in hippocampal synaptic plasticity. Anesthesia/surgery induced a reduction of GDNF, which was colocalized with astrocytes. Overexpression of GDNF in astrocytes could ameliorate the decline in cognitive function by improving hippocampal synaptic plasticity, meanwhile astrocytic GDNF rescued the anesthesia/surgery-induced decrease in GFRα1 and NCAM.

CONCLUSION

The study concludes that astrocytic GDNF may improve anesthesia/surgery-induced cognitive impairment by promoting hippocampal synaptic plasticity in aged mice via the GFRα1/NCAM pathway.

Single exposure to anesthesia/surgery in neonatal mice induces cognitive impairment in young adult mice

BACKGROUND

The effects of a solitary neonatal exposure to anesthesia plus surgery (anesthesia/surgery) on cognitive function and the underlying mechanism in developing brains remains largely undetermined. We, therefore, set out to investigate the impact of single exposure to anesthesia/surgery in neonatal mice.

METHODS

Six-day-old male and female mice received abdominal surgery under 3% sevoflurane plus 50% oxygen for 2 h. The new object recognition (NOR) and Morris water maze (MWM) were used to evaluate cognitive function in young adult mice. Western blot, ELISA and RT-PCR were used to measure levels of NR2B and IL-6 in medial prefrontal cortex and IL-6 in blood of the mice. We employed NR2B siRNA and IL-6 antibody in the interaction studies.

RESULTS

The anesthesia/surgery decreased the ratio of novel time to novel plus familiar time in NOR and the number of platform crossings, but not escape latency, in MWM compared to sham condition. The mice in anesthesia/surgery group had increased NR2B expression in medial prefrontal cortex, and IL-6 amounts in blood and medial prefrontal cortex. Local injection of NR2B siRNA in medial prefrontal cortex alleviated the anesthesia/surgery-induced cognitive impairment. IL-6 antibody mitigated the anesthesia/surgery-induced upregulation of NR2B and cognitive impairment in young adult mice.

CONCLUSIONS

These results suggest that a single neonatal exposure to anesthesia/surgery causes impairment of memory, but not learning, in young adult mice through IL-6-regulated increases in NR2B concentrations in medial prefrontal cortex, highlighting the need for further research on the underlying mechanisms of anesthesia/surgery's impact on cognitive function in developing brains.

Protective Effect of the SIRT1-Mediated NF-κB Signaling Pathway against Necrotizing Enterocolitis in Neonatal Mice

OBJECTIVE

 To discover the mechanism of the sirtuin 1 (SIRT1)-mediated nuclear factor-κB (NF-κB) pathway in the protection against necrotizing enterocolitis (NEC) in neonatal mice.

MATERIALS AND METHODS

 Neonatal mice were treated with EX527 (an inhibitor of SIRT1) and/or pyrrolidine dithiocarbamate (PDTC, an inhibitor of NF-κB). The survival rate of the mice was recorded. Hematoxylin and eosin (HE) staining was performed to observe the pathological changes in the intestines. Furthermore, western blotting, enzyme-linked immunosorbent assay, and real-time quantitative polymerase chain reaction were conducted to measure the protein and gene expression, while corresponding kits were used to detect the levels of oxidative stress indicators.

RESULTS

 PDTC increased the survival rate of NEC mice. When compared with the NEC+ EX527 + PDTC group, the histological NEC score was higher in the NEC + EX527 group but lower in the NEC + PDTC group. SIRT1 expression in the intestines of NEC mice was downregulated, with an increase in p65 nuclear translocation. Additionally, malondialdehyde increased and glutathione peroxidase decreased in the intestines of NEC mice, with the upregulation of interleukin (IL)-6, IL-1β, and tumor necrosis factor-α, as well as the downregulation of ZO-1, occludin, and claudin-4 in the intestines. However, the above changes could be improved by PDTC, which could be further reversed by EX527.

CONCLUSION

 SIRT1 can mitigate inflammation and the oxidative stress response and improve intestinal permeability by mediating the NF-κB pathway, playing an important role in the alleviation of NEC.

Postoperative Learning and Memory Dysfunction Is More Severe in Males But Is Not Persistent and Transmittable to Next Generation in Young Adult Rats

BACKGROUND

Postoperative cognitive dysfunction (POCD) affects numerous patients each year and is associated with poor outcomes. Currently, the duration of POCD is not known. This preclinical study determined whether POCD was persistent, different between sexes and transmittable to the next generation.

METHODS

Two-month-old Sprague-Dawley rats had left carotid artery exposure under isoflurane anesthesia and their learning and memory were assessed from 5 days, 2 months, and 4 months after surgery. Rats with or without surgery were mated when they were 4 or 6 months old, and the learning and memory of the offspring were tested at 2 months of age.

RESULTS

Males exposed to surgery took a longer time to identify the target box after training sessions in a Barnes maze and had less freezing behavior in context-related fear conditioning than control rats when the tests were started 5 days after surgery. Similarly, female rats had a poorer performance than control rats in the Barnes maze test from 5 days after surgery. However, these poorer performances were not observed when the tests were administered 2 or 4 months after surgery. The offspring of rats with surgery had a performance similar to that of the offspring of control rats.

CONCLUSIONS

Our results suggest that both male and female rats develop POCD but that the learning and memory dysfunction appears to be more severe in male rats. POCD may not be persistent and does not transmit to the next generation.

Effects of gestational inflammation on age-related cognitive decline and hippocampal Gdnf-GFRα1 levels in F1 and F2 generations of CD-1 Mice

BACKGROUND

It has been reported that age-associated cognitive decline (AACD) accelerated by maternal lipopolysaccharide (LPS) insult during late pregnancy can be transmitted to the second generation in a sex-specificity manner. In turn, recent studies indicated that glial cell line-derived neurotrophic factor (GDNF) and its cognate receptor (GFRα1) are critical for normal cognitive function. Based on this evidence, we aimed to explore whether Gdnf-GFRα1 expression contributes to cognitive decline in the F1 and F2 generations of mouse dams exposed to lipopolysaccharide (LPS) during late gestation, and to evaluate also the potential interference effect of pro-inflammatory cytokines.

METHODS

During gestational days 15-17, pregnant CD-1 mice (8-10 weeks old) received a daily intraperitoneal injection of LPS (50 μg/kg) or saline (control). In utero LPS-exposed F1 generation mice were selectively mated to produce F2 generation mice. In F1 and F2 mice aged 3 and 15 months, the Morris water maze (MWM) was used to evaluated the spatial learning and memory ability, the western blotting and RT-PCR were used for analyses of hippocampal Gdnf and GFRα1 expression, and ELISA was used to analyse IL-1β, IL-6 and TNF-α levels in serum.

RESULTS

Middle-aged F1 offspring from LPS-treated mothers exhibited longer swimming latency and distance during the learning phase, lower percentage swimming time and distance in targe quadrant during memory phase, and lower hippocampal levels of Gdnf and GFRα1 gene products compared to age-matched controls. Similarly, the middle-aged F2 offspring from the Parents-LPS group had longer swimming latency and distance in the learning phase, and lower percentage swimming time and distance in memory phase than the F2-CON group. Moreover, the 3-month-old Parents-LPS and 15-month-old Parents- and Father-LPS groups had lower GDNF and GFRα1 protein and mRNAs levels compared to the age-matched F2-CON group. Furthermore, hippocampal levels of Gdnf and GFRα1 were correlated with impaired cognitive performance in the Morris water maze after controlling for circulating pro-inflammatory cytokine levels.

CONCLUSIONS

Our findings indicate that accelerated AACD by maternal LPS exposure can be transmitted across at least two generations through declined Gdnf and GFRα1 expression, mainly via paternal linage.

Effect of sevoflurane anesthesia to neonatal rat hippocampus by RNA-seq

BACKGROUND

Sevoflurane is an inhalational anesthetic for the induction and maintenance of general anesthesia in pediatric surgery. However, few studies have paid attention to the multiple organ toxicity and the mechanism behind it.

METHODS

Inhalation anesthesia neonatal rat model were realized by exposing to 3.5% sevoflurane. RNA-seq was performed to find out how inhalation anesthesia affects the lung, cerebral cortex, hippocampus, and heart. Validation of RNA-seq results by QPCR after animal model establishment. Tunel assay detects cell apoptosis in each group. CCK-8, cell apoptosis assay and western blot assay validation of the role of siRNA-Bckdhb in the action of sevoflurane on rat hippocampal neuronal cells.

RESULTS

There are significant differences between different groups, especially the hippocampus and cerebral cortex. Bckdhb was significantly up-regulated in the hippocampus with sevoflurane-treated. Pathway analysis revealed several abundant pathways related to DEGs, e.g., protein digestion and absorption and PI3K-Akt signaling pathway. A series of cellular and animal experiments showed that siRNA-Bckdhb can inhibit the reduction of cellular activity caused by sevoflurane.

CONCLUSION

Bckdhb interference experiments indicated that sevoflurane induces hippocampal neuronal cells apoptosis by regulating Bckdhb expression. Our study provided new insights into the molecular mechanism of sevoflurane-induced brain damage in pediatrics.

Minocycline Attenuates Sevoflurane-Induced Postoperative Cognitive Dysfunction in Aged Mice by Suppressing Hippocampal Apoptosis and the Notch Signaling Pathway-Mediated Neuroinflammation

Postoperative cognitive dysfunction (POCD), an important postoperative neurological complication, is very common and has an elevated incidence in elderly patients. Sevoflurane, an inhaled anesthetic, has been demonstrated to be associated with POCD in both clinical and animal studies. However, how to prevent POCD remains unclear. Minocycline, a commonly used antibiotic can cross the blood-brain barrier and exert an inhibitory effect on inflammation in the central nervous system. The present work aimed to examine the protective effect and mechanism of minocycline on sevoflurane-induced POCD in aged mice. We found that 3% sevoflurane administered 2 h a day for 3 consecutive days led to cognitive impairment in aged animals. Further investigation revealed that sevoflurane impaired synapse plasticity by causing apoptosis and neuroinflammation and thus induced cognitive dysfunction. However, minocycline pretreatment (50 mg/kg, i.p, 1 h prior to sevoflurane exposure) significantly attenuated learning and memory impairments associated with sevoflurane in aged animals by suppressing apoptosis and neuroinflammation. Moreover, a mechanistic analysis showed that minocycline suppressed sevoflurane-triggered neuroinflammation by inhibiting Notch signaling. Similar results were also obtained in vitro. Collectively, these findings suggested minocycline may be an effective drug for the prevention of sevoflurane-induced POCD in elderly patients.

Inhibition of ERK/CREB signaling contributes to postoperative learning and memory dysfunction in neonatal rats

Exposure to surgery with anesthesia early in life may lead to abnormal behavior, learning, and memory in humans. Pre-clinical studies have suggested a critical role of glial cell-derived neurotrophic factor (GDNF) in these effects. We hypothesize that the inhibition of extracellular signal-regulated kinase (ERK)-cAMP response element-binding protein (CREB) pathway contributes to GDNF decrease and the dysfunction of learning and memory. To address this hypothesis, 7-day-old Sprague-Dawley male and female rats were subjected to right carotid artery exposure (surgery) under sevoflurane anesthesia. Their learning and memory were tested by the Barnes maze, and novel object recognition tests started 23 days after the surgery. Blood and brain were harvested at various times after surgery for biochemical analyses. Rats with surgery and anesthesia performed poorly in the Barnes maze and novel object recognition tests compared with control rats. Rats with surgery had a decreased GDNF concentration in the brain and urine. The concentrations of urine GDNF were negatively correlated with the performance of rats in a delayed memory phase of the Barnes maze test. Surgery increased proinflammatory cytokines in the blood and brain. Intracerebroventricular injection of GDNF attenuated the increased inflammatory response in surgery rats. Surgery inhibited ERK and CREB. Inhibiting ERK reduced GDNF and induced poor performance in the Barnes maze and novel object recognition tests of rats without surgery. Surgery also increased brain-derived natriuretic peptide (BNP) in the brain. Intracerebroventricular injection of BNP inhibited ERK and CREB, reduced GDNF, and impaired learning and memory. Surgery, ERK inhibition, and BNP reduced the expression of synaptic proteins. Our results suggest that surgery increases BNP that inhibits ERK-CREB signaling to reduce GDNF, which leads to an unbalanced inflammatory response and a reduced synaptic protein expression for the development of postoperative cognitive dysfunction. KEY MESSAGES: Surgery increases BNP and decreases ERK/CREB signaling to reduce GDNF. The increase in BNP and decrease in ERK/CREB signaling contribute to postoperative cognitive dysfunction. GDNF reduction contributes to neuroinflammatory response after surgery. Urine GDNF concentrations are negatively corrected with poor spatial memory performance.

Serum glial cell line-derived neurotrophic factor (GDNF) a potential biomarker of executive function in Parkinson's disease

Objective

Evidence shows that the impairment of executive function (EF) is mainly attributed to the degeneration of frontal-striatal dopamine pathway. Glial cell line-derived neurotrophic factor (GDNF), as the strongest protective neurotrophic factor for dopaminergic neurons (DANs), may play a role in EF to some extent. This study mainly explored the correlation between serum GDNF concentration and EF performance in Parkinson's disease (PD).

Methods

This study recruited 45 healthy volunteers (health control, HC) and 105 PD patients, including 44 with mild cognitive impairment (PD-MCI), 20 with dementia (PD-D), and 20 with normal cognitive function (PD-N). Neuropsychological tests were performed to evaluate EF (working memory, inhibitory control, and cognitive flexibility), attention, language, memory, and visuospatial function. All subjects were tested for serum GDNF and homovanillic acid (HVA) levels by ELISA and LC-ESI-MS/MS, respectively.

Results

PD-MCI patients showed impairments in the trail making test (TMT) A (TMT-A), TMT-B, clock drawing test (CDT) and semantic fluency test (SFT), whereas PD-D patients performed worse in most EF tests. With the deterioration of cognitive function, the concentration of serum GDNF and HVA in PD patients decreased. In the PD group, the serum GDNF and HVA levels were negatively correlated with TMT-A (r _GDNF = -0.304, P < 0.01; r _HVA = -0.334, P < 0.01) and TMT-B (r _GDNF = -0.329, P < 0.01; r _HVA = -0.323, P < 0.01) scores. Serum GDNF levels were positively correlated with auditory verbal learning test (AVLT-H) (r = 0.252, P < 0.05) and SFT (r = 0.275, P < 0.05) scores. Serum HVA levels showed a positively correlation with digit span test (DST) (r = 0.277, P < 0.01) scores. Stepwise linear regression analysis suggested that serum GDNF and HVA concentrations and UPDRS-III were the influence factors of TMT-A and TMT-B performances in PD patients.

Conclusion

The decrease of serum GDNF concentration in PD patients was associated with impaired inhibitory control, cognitive flexibility, and attention performances. The changes of GDNF and HVA might synergistically participate in the occurrence and development of executive dysfunction in PD patients.

Early preterm infant microbiome impacts adult learning

Interventions to mitigate long-term neurodevelopmental deficits such as memory and learning impairment in preterm infants are warranted. Manipulation of the gut microbiome affects host behaviors. In this study we determined whether early maturation of the infant microbiome is associated with neurodevelopment outcomes. Germ free mice colonized at birth with human preterm infant microbiomes from infants of advancing post menstrual age (PMA) demonstrated an increase in bacterial diversity and a shift in dominance of taxa mimicking the human preterm microbiome development pattern. These characteristics along with changes in a number of metabolites as the microbiome matured influenced associative learning and memory but not locomotor ability, anxiety-like behaviors, or social interaction in adult mice. As a regulator of learning and memory, brain glial cell-derived neurotrophic factor increased with advancing PMA and was also associated with better performance in associative learning and memory in adult mice. We conclude that maturation of the microbiome in early life of preterm infants primes adult associative memory and learning ability. Our findings suggest a critical window of early intervention to affect maturation of the preterm infant microbiome and ultimately improve neurodevelopmental outcomes.

Glial cell-derived neurotrophic factor decrease may mediate learning, memory and behavior impairments in rats after neonatal surgery

Patients who have surgery during the first few years of their lives may have an increased risk of behavioral abnormality. Our previous study has shown a role of glial cell-derived neurotrophic factor (GDNF) in neonatal surgery-induced learning and memory impairment in rats. This study was designed to determine whether neonatal surgery induced hyperactive behavior in addition to learning and memory impairment and whether GDNF played a role in these changes. Postnatal day 7 male and female Sprague-Dawley rats were subjected to right common carotid arterial exposure under sevoflurane anesthesia. Their learning, memory and behavior were tested from 23 days after the surgery. GDNF was injected intracerebroventricularly at the end of surgery. Surgery reduced GDNF expression in the hippocampus. Surgery impaired learning and memory and induced a hyperactive behavior as assessed by Barnes maze, fear conditioning and open field tests. In addition, surgery reduced dendritic arborization and spine density. The effects were attenuated by GDNF injection. These results suggest that surgery induces a hyperactive behavior pattern, impairment of learning and memory, and neuronal microstructural damage later in the lives in rats. GDNF reduction may mediate these surgical effects.

General Anesthesia in the First 36 Months of Life–a Study of Cognitive Performance in Children Aged 7-11 Years (ANFOLKI-36)

BACKGROUND

Experimental data have shown that the developing brain is especially vulnerable to exogenous noxious substances. The potential effects of anesthetic drugs on brain growth and development are a matter of concern. Clinical studies of children who underwent general anesthesia in their earliest years can make a major contribution to our understanding of the effects of anesthetic drugs on infants and toddlers (i.e., children under age 5).

METHODS

Children born at term during the years 2007-2011 who were exposed to general anesthesia before their third birthday were included in the study. Data on general anesthesia were retrospectively evaluated, and the overall intelligence quotient (IQ) was determined prospectively as the primary target parameter. Children who had not been exposed to general anesthesia were recruited as a control group. The non-inferiority threshold was set at a difference of 5 IQ points out of a consideration of clinical relevance.

RESULTS

430 complete data sets were available from exposed children and 67 from members of the control group. The exposed group achieved a mean IQ score of 108.2, with a 95% confidence interval of [107; 109.4]; the corresponding values in the control group were 113 [110; 116.1]. Both groups achieved a mean score that was higher than the expected 100 points. After adjustment for age, socioeconomic status, and sex, the difference between the two groups was 2.9 points [0.2; 5.6], indicating a significantly better outcome in the control group than in the exposed group. The non-inferiority threshold of 5 IQ points was within the confidence interval; thus, non-inferiority was not demonstrated.

CONCLUSION

The fact that both groups achieved a higher IQ score than the expected 100 points may be attributable, at least in part, to the restriction of the study to children born at term. The results indicate that general anesthesia in early childhood is not associated with markedly reduced intelligence in later years, although non-inferiority could not be demonstrated.

LncRNA Riken Attenuated Sevoflurane-Induced Neuroinflammation by Regulating the MicroRNA-101a/MKP-1/JNK Pathway

The induction of anesthesia in children makes its safety one of the most important global health problems. Neuroinflammation contributes to anesthesia-induced neurotoxicity in young individuals. However, the mechanisms underlying anesthesia-induced neurotoxicity have not been established. In this study, the level of interleukin (IL)-6 in the hippocampus of mice and N2A cells treated with sevoflurane was increased, and long noncoding RNA (LncRNA) Riken was sufficient to decrease sevoflurane-induced neurotoxicity, and the level of inflammatory cytokine IL-6. The RNA pull-down assay verified that miR-101a was bound to lncRNA Riken in N2A cells. In addition, miR-101a blocked the protective effect of lncRNA Riken on anesthesia-induced neuroinflammation. These data suggest that lncRNA Riken attenuated anesthesia-induced neuroinflammation by interacting with microRNA-101a. Finally, we also demonstrated that MAPK phosphatase 1 (MKP-1) was a downstream target of miR-101a, and lncRNA Riken can regulate the expression of MKP-1; the JNK signal transduction pathway has been implicated in sevoflurane-induced IL-6 secretion. Our findings demonstrated that lncRNA Riken alleviated the sevoflurane-induced neurotoxic effects, and the lncRNA Riken/miR-101a/MKP-1/JNK axis plays an important role in the cognitive disorder.

Evaluating memory dysfunction after spinal anesthesia among patients undergoing elective surgery: Descriptive-analytical study

BACKGROUND

Anesthesia has a number of side effects including cognitive impairment after the surgery. Postoperative cognitive impairment is commonly associated with general anesthesia.

OBJECTIVE

The aim of this study is to evaluate the effects of Marcaine (bupivacaine hydrochloride) in memory impairment among patients undergoing elective surgery.

MATERIALS AND METHODS

In this study descriptive-analytical study, patients undergoing elective lower extremity or lower abdomen surgery requiring spinal anesthesia were included. Following 24 h of the surgery, standard Wechsler questionnaire was used to assess memory of the patients. Other demographic and clinical parameters such as age, gender and blood pressure, pulse rate were also recorded. The obtained data was analyzed using SPSSv18.

RESULTS

In this study, 105 patients where 55 (52.4%) males and 50 (47.6%) females were studied. The mean age of the subjects was 35.73 ± 10.64 years. There was a significant difference between the mean of memory scores in terms of logical memory and overall memory (P < 0.001). There was a significant relationship between the mean scores of patients' rational memory and systolic blood pressure at admission (P = 0.030). There was a significant relationship between mean associative learning scores in patients and systolic blood pressure at admission (P = 0.046) and type of surgery (P = 0.013). Furthermore, overall memory scores were significantly associated with age (P = 0.041).

CONCLUSION

Based on the results of this study, it can be concluded that spinal anesthesia had a significant effect on some areas of memory. Further studies in this area can yield more reliable results.

Possible role of glial cell line-derived neurotrophic factor for predicting cognitive impairment in Parkinson's disease: a case-control study

Glial cell line-derived neurotrophic factor (GDNF) plays an important role in the protection of dopaminergic neurons, but there are few reports of the relationship between GDNF and its precursors (α-pro-GDNF and β-pro-GDNF) and cognitive impairment in Parkinson’s disease. This study aimed to investigate the relationship between the serum levels of GDNF and its precursors and cognitive impairment in Parkinson’s disease, and to assess their potential as a diagnostic marker. Fifty-three primary outpatients and hospitalized patients with Parkinson’s disease (23 men and 30 women) with an average age of 66.58 years were enrolled from the Affiliated Hospital of Xuzhou Medical University of China in this case-control study. The patients were divided into the Parkinson’s disease with cognitive impairment group (n = 27) and the Parkinson’s disease with normal cognitive function group (n = 26) based on their Mini-Mental State Examination, Montreal Cognitive Assessment, and Clinical Dementia Rating scores. In addition, 26 age- and sex-matched healthy subjects were included as the healthy control group. Results demonstrated that serum GDNF levels were significantly higher in the Parkinson’s disease with normal cognitive function group than in the other two groups. There were no significant differences in GDNF precursor levels among the three groups. Correlation analysis revealed that serum GDNF levels, GDNF/α-pro-GDNF ratios, and GDNF/β-pro-GDNF ratios were moderately or highly correlated with the Mini-Mental State Examination, Montreal Cognitive Assessment, and Clinical Dementia Rating scores. To explore the risk factors for cognitive impairment in patients with Parkinson’s disease, logistic regression analysis and stepwise linear regression analysis were performed. Both GDNF levels and Hoehn-Yahr stage were risk factors for cognitive impairment in Parkinson’s disease, and were the common influencing factors for cognitive scale scores. Neither α-pro-GDNF nor β-pro-GDNF was risk factors for cognitive impairment in Parkinson’s disease. A receiver operating characteristic curve of GDNF was generated to predict cognitive function in Parkinson’s disease (area under the curve = 0.859). This result indicates that the possibility that serum GDNF can correctly distinguish whether patients with Parkinson’s disease have cognitive impairment is 0.859. Together, these results suggest that serum GDNF may be an effective diagnostic marker for cognitive impairment in Parkinson’s disease. However, α-pro-GDNF and β-pro-GDNF are not useful for predicting cognitive impairment in this disease. This study was approved by Ethics Committee of the Affiliated Hospital of Xuzhou Medical University, China (approval No. XYFY2017-KL047-01) on November 30, 2017.

Appropriate exercise level attenuates gut dysbiosis and valeric acid increase to improve neuroplasticity and cognitive function after surgery in mice

Postoperative cognitive dysfunction (POCD) affects the outcome of millions of patients each year. Aging is a risk factor for POCD. Here, we showed that surgery induced learning and memory dysfunction in adult mice. Transplantation of feces from surgery mice but not from control mice led to learning and memory impairment in non-surgery mice. Low intensity exercise improved learning and memory in surgery mice. Exercise attenuated surgery-induced neuroinflammation and decrease of gut microbiota diversity. These exercise effects were present in non-exercise mice receiving feces from exercise mice. Exercise reduced valeric acid, a gut microbiota product, in the blood. Valeric acid worsened neuroinflammation, learning and memory in exercise mice with surgery. The downstream effects of exercise included attenuating growth factor decrease, maintaining astrocytes in the A2 phenotypical form possibly via decreasing C3 signaling and improving neuroplasticity. Similar to these results from adult mice, exercise attenuated learning and memory impairment in old mice with surgery. Old mice receiving feces from old exercise mice had better learning and memory than those receiving control old mouse feces. Surgery increased blood valeric acid. Valeric acid blocked exercise effects on learning and memory in old surgery mice. Exercise stabilized gut microbiota, reduced neuroinflammation, attenuated growth factor decrease and preserved neuroplasticity in old mice with surgery. These results provide direct evidence that gut microbiota alteration contributes to POCD development. Valeric acid is a mediator for this effect and a potential target for brain health. Low intensity exercise stabilizes gut microbiota in the presence of insult, such as surgery.

Amantadine Alleviates Postoperative Cognitive Dysfunction Possibly by Preserving Neurotrophic Factor Expression and Dendritic Arborization in the Hippocampus of Old Rodents

Objectives

Amantadine has been shown to attenuate postoperative learning and memory dysfunction in young adult rats. However, postoperative cognitive dysfunction often occurs in elderly patients. We aimed to determine whether amantadine attenuated postoperative learning and memory dysfunction and whether these effects were associated with improved dendritic arborization in old rodents.

Methods

Eighteen-month old male C57BL/6J mice or Fischer 344 rats were subjected to right carotid artery exposure (surgery) under isoflurane anesthesia. This age represents an early old stage in rodents. Carotid artery exposure was used to simulate commonly performed carotid endarterectomy in elderly patients. Amantadine was injected intraperitoneally at 25 μg/g once a day for 3 days with the first dose at 15 min before surgery. The animals were tested by Barnes maze and fear conditioning starting one week after the surgery. Hippocampus was harvested for Western blotting and Golgi staining.

Results

Surgery and anesthesia impaired the learning and memory in old mice and rats. Surgery reduced the expression of brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF), dendritic arborization and spine density in the hippocampus of old rats. These effects were attenuated by amantadine. The effects of amantadine were blocked by intracerebroventricular injection of anti-BDNF antibody or anti-GDNF antibody.

Conclusion

Surgery and anesthesia impaired learning, memory and dendritic arborization in old rodents that are age relevant to postoperative cognitive dysfunction. These effects may be attenuated by amantadine via preserving the expression of neurotrophic factors.

Laminin degradation by matrix metalloproteinase 9 promotes ketamine-induced neuronal apoptosis in the early developing rat retina

AIMS

During early development, laminin degradation contributes to the death of neurons. This study aims to investigate the role and regulation of laminin in ketamine-induced apoptosis.

METHODS

We performed terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) and immunohistochemical assays to investigate the roles of the non-integrin laminin receptor, matrix metalloproteinase 9 (MMP9) in ketamine-induced neuronal apoptosis. In situ zymography, Western blot, and immunofluorescence were used to explore the relationships between laminin, MMP9 activity, and Zn2+ . Experiments were performed using whole-mount retinas dissected from Sprague Dawley rats.

RESULTS

The TUNEL and immunohistochemical assays indicated that ketamine-induced neuronal apoptosis in early developing rat retina. Blockade of non-integrin laminin receptor promoted ketamine-induced apoptosis, while non-integrin laminin receptor activation attenuated ketamine-induced apoptosis. Ketamine-induced laminin degradation, possibly by enhancing the activity of MMP9. MMP9 inhibition reduced ketamine-induced apoptosis by reducing laminin degradation. Downregulation of Zn2+ attenuated the increased MMP9 activity, laminin degradation caused by ketamine and significantly reduced ketamine-induced neuronal apoptosis.

CONCLUSION

Laminin degradation by MMP9 promoted ketamine-induced neuronal apoptosis in early developing rat retina. The non-integrin laminin receptor may be a pathway involved in ketamine-induced apoptosis. Zn2+ downregulation may play a protective role against ketamine-induced neuronal apoptosis through inhibiting MMP9 activity.

Research progress and treatment strategies for anesthetic neurotoxicity

Every year, a large number of infants and young children worldwide are administered general anesthesia. Whether general anesthesia adversely affects the intellectual development and cognitive function of children at a later date remains controversial. Many animal experiments have shown that general anesthetics can cause nerve damage during development, affect synaptic plasticity, and induce apoptosis, and finally affect learning and memory function in adulthood. The neurotoxicity of pediatric anesthetics (PAN) has received extensive attention in the field of anesthesia, which has been listed as a potential problem affecting public health by NFDA of the United States. Previous studies on rodents and non-human primates indicate that inhalation of anesthetics early after birth can induce long-term and sustained impairment of learning and memory function, as well as changes in brain function. Many anti-oxidant drugs, dexmedetomidine, as well as a rich living environment and exercise have been proven to reduce the neurotoxicity of anesthetics. In this paper, we summarize the research progress, molecular mechanisms and current intervention measures of anesthetic neurotoxicity.

Learning and memory dysfunction of non-surgery cage-mates of mice with surgery

A patient can develop cognitive dysfunction and neuroinflammation after surgery. However, it is not known whether these pathological processes occur in people who live together with surgery patients. As an initial step to address this issue in animals, 2 mice with right common carotid arterial exposure were cage-mates with 3 non-surgery mice. Their learning and memory were tested starting 5 days after surgery. Their brain tissues were harvested 1 day or 5 days after surgery. The results showed that mice with surgery and cage-mates of these surgery mice had increased pro-inflammatory cytokines in the brain and dysfunction of learning and memory. Inhibition of inflammation attenuated the cognitive impairment of the cage-mates. These results suggest that dysfunction of complex behavior including learning and memory can occur in non-surgery cage-mates of surgery mice. Additional studies are needed to determine whether this phenomenon exists in larger animals and humans.

Histone Deacetylases May Mediate Surgery-Induced Impairment of Learning, Memory, and Dendritic Development

Postoperative cognitive dysfunction (POCD) affects millions of patients each year in the USA and has been recognized as a significant complication after surgery. Epigenetic regulation of learning and memory has been shown. For example, an increase of histone deacetylases (HDACs), especially HDAC2, which epigenetically regulates gene expression, impairs learning and memory. However, the epigenetic contribution to the development of POCD is not known. Also, the effects of living situation on POCD have not been investigated. Here, we showed that mice that lived alone before the surgery and lived in a group after the surgery and mice that lived in a group before surgery and lived alone after surgery had impairment of learning and memory compared with the corresponding control mice without surgery. Surgery increased the activity of HDACs including HDAC2 but not HDAC1 and decreased brain-derived neurotrophic factor (BDNF), dendritic arborization, and spine density in the hippocampus. Suberanilohydroxamic acid (SAHA), a relatively specific inhibitor of HDAC2, attenuated these surgery effects. SAHA did not change BDNF expression, dendritic arborization, and spine density in mice without surgery. Surgery also reduced the activity of nuclear histone acetyltransferases (HATs). This effect was not affected by SAHA. Our results suggest that surgery activates HDACs, which then reduces BDNF and dendritic arborization to develop POCD. Thus, epigenetic change contributes to the occurrence of POCD.

Sevoflurane Induces Hippocampal Neuronal Apoptosis by Altering the Level of Neuropeptide Y in Neonatal Rats

Numerous studies have shown that the inhaled general anesthetic sevoflurane imposes toxicity on the central nervous system during the developmental period but the underlying mechanisms remain unclear. Neuropeptide Y (NPY) was reported to have important neuroprotective effects, which can attenuate neuronal loss under pathological conditions. However, the effects of NPY on sevoflurane-induced hippocampal neuronal apoptosis have not been investigated. In this study, postnatal day 7 (PND7) Sprague-Dawley rats and primary cultured cells separated from hippocampi were exposed to sevoflurane (2.4% for 4 h) and the NPY expression levels after treatment were analyzed. Furthermore, neuronal apoptosis assay was conducted via immunofluorescence staining of cleaved caspase-3 and flow cytometry after exogenous NPY administration to PND7 rats as well as cultured hippocampal neurons to elucidate the role of NPY in sevoflurane-induced neurotoxicity. Our results showed the level of NPY gradually decreased within 24 h after sevoflurane exposure in both the hippocampus of PND7 rats and cultured hippocampal neurons, but not in cultured astrocytes. In the exogenous NPY pretreatment study, the proportion of cleaved caspase-3 positive cells in the CA1 region of the hippocampus was increased significantly at 24 h after sevoflurane treatment, while NPY pretreatment could reduce it. Similarly, NPY could also reverse the apoptogenic effect of sevoflurane on cultured neurons. Herein, our results showed that sevoflurane caused a significant decrease in NPY expression, whereas exogenous NPY supplementation could reduce sevoflurane-induced hippocampal neuronal apoptosis both in vivo and in vitro.

Serum levels of glial cell line-derived neurotrophic factor and multiple neurotransmitters: In relation to cognitive performance in Parkinson's disease with mild cognitive impairment

OBJECTIVES

Mild cognitive impairment is a common non-motor feature of Parkinson's disease, termed PD-MCI. But there is a scarcity of data on the role of glial cell line-derived neurotrophic factor (GDNF) and neurotransmitters in pathogenesis of PD-MCI. The aim of this project was to detect the serum levels of GDNF and multiple neurotranmitters and explore their relationships with cognitive performance in PD-MCI patients.

METHODS

Neuropsychological testing was administered to PD patients and healthy controls to investigate different domains of cognitive function. Serum levels of GDNF and four cognition-related neurotransmitters including Dopamine metabolites Homovanillic acid (HVA), acetylcholine (Ach), γ-aminobutyric acid (GABA) and 5-hydroxytryptamine (5-HT) were detected by enzyme-linked immunosorbent assay and liquid chromatography-electrospray ionization tandem mass spectrometry analysis respectively.

RESULTS

The more serious cognitive impairment of PD, the lower levels of GDNF, HVA and 5-HT. In PD-MCI patients, the levels of GDNF, HVA, Ach, 5-HT, and GABA had a significant positive correlation with Digit span backward test (DSB-T) scores and negative correlation with the scores of Trail Making Test A (TMT-A) and Trail Making Test B (TMT-B) respectively. Effect size analysis showed that GDNF and GDNF*Ach have a significant effect on DSB-T, TMT-A and TMT-B respectively; GDNF*HVA, GDNF*5-HT and GDNF*GABA play important part in Auditory Verbal Learning Test separately.

CONCLUSIONS

Serum GDNF may be involved in the impairment of attention, memory and executive function of PD-MCI patients, by acting alone or in conjunction with neurotransmitters (HVA, 5-HT, GABA, and Ach).

Intranasal Administration of Insulin Reduces Chronic Behavioral Abnormality and Neuronal Apoptosis Induced by General Anesthesia in Neonatal Mice

Children, after multiple exposures to general anesthesia, appear to be at an increased risk of developing learning disabilities. Almost all general anesthetics—including sevoflurane, which is commonly used for children—are potentially neurotoxic to the developing brain. Anesthesia exposure during development might also be associated with behavioral deficiencies later in life. To date, there is no treatment to prevent anesthesia-induced neurotoxicity and behavioral changes. In this study, we anesthetized 7-day-old neonatal mice with sevoflurane for 3 h per day for three consecutive days and found that the anesthesia led to mild behavioral abnormalities later in life that were detectable by using the novel object recognition test, Morris water maze, and fear conditioning test. Biochemical and immunohistochemical studies indicate that anesthesia induced a decrease in brain levels of postsynaptic density 95 (PSD95), a postsynaptic marker, and marked activation of neuronal apoptosis in neonatal mice. Importantly, insulin administered through intranasal delivery prior to anesthesia was found to prevent the anesthesia-induced long-term behavioral abnormalities, reduction of PSD95, and activation of neuronal apoptosis. These findings suggest that intranasal insulin administration could be an effective approach to prevent the increased risk of neurotoxicity and chronic damage caused by anesthesia in the developing brain.

LncRNA MIAT overexpression reduced neuron apoptosis in a neonatal rat model of hypoxic-ischemic injury through miR-211/GDNF

OBJECTIVE

To investigate the underlying mechanism of lncRNA myocardial infarction-associated transcript (MIAT) in hypoxic-ischemic (HI)-induced neonatal cerebral palsy.

MATERIALS AND METHODS

Neonatal rat model of HI injury was established to detect the motor function. LncRNA MIAT, miR-211, glial cell line-derived neurotrophic factor (GDNF) and caspase-3 expressions were measured by qRT-PCR or western blot. The apoptosis of Neuro2A cells was detected by flow cytometry. RNA immunoprecipitation (RIP) and RNA pull-down assays were performed to confirm the interaction between MIAT and miR-211.

RESULTS

Compared with control group, lncRNA MIAT and GDNF were downregulated in striatal tissues of neonatal rats in HI group and oxygen glucose deprivation (OGD)-induced ischemic injury of Neuro2A cells, whereas miR-211 was up-regulated in striatal tissues of HI group and OGD-induced ischemic injury of Neuro2A cells. LncRNA MIAT interacted with miR-211, and lncRNA MIAT overexpression reduced neuron apoptosis through miR-211. Besides, GDNF expression was positively regulated by lncRNA MIAT and negatively regulated by miR-211 in Neuro2A cells. In vivo experiment proved MIAT promoted motor function and relieved HI injury.

CONCLUSION

MIAT overexpression reduced apoptosis of Neuro2A cells through miR-211/GDNF, which relieved HI injury of neonatal rats.

Short- and Long-Term Protective Effects of Melatonin in a Mouse Model of Sepsis-Associated Encephalopathy

Brain dysfunction is a common complication after sepsis and is an independent risk factor for a poor prognosis, which is partly attributed to the dysregulated inflammatory response and oxidative damage. Melatonin regulates the sleep-wake cycle and also has potent anti-inflammatory and antioxidant properties, yet the protective effects of melatonin on sepsis-induced neurobehavioral dysfunction remain to be elucidated. In the present study, melatonin was administered intraperitoneally daily at a dose of 10 mg/kg for three consecutive days immediately (early treatment) or 7 days (delayed treatment) after sham operation or cecal ligation and puncture (CLP), followed by an additional treatment in drinking water until the end of behavioral tests. The concentrations of pro-inflammatory cytokines (tumor necrosis factor (TNF-α), interleukin-1β (IL-1β), IL-6, IL-10), malondialdehyde (MDA), superoxide dismutase (SOD), reactive oxygen species (ROS), brain-derived neurotrophic factor (BDNF), and glial cell line-derived neurotrophic factor (GDNF) were determined at the indicated time points. Compared with the CLP + vehicle group, we found that early melatonin treatment resulted in increased survival rate but not improvement in measures of neurobehavioral outcomes, which was accompanied by significantly lower plasma level of IL-1β. Intriguingly, delayed melatonin treatment improved neurobehavioral dysfunction by normalization of hippocampal BDNF and GDNF expressions. In conclusion, our study suggests the beneficial effects of both early and delayed melatonin treatment after sepsis development, which implicates melatonin has a potential therapeutic value in sepsis-associated organ damage including brain dysfunction.